SOIiE PHOTOINDUCED DECARBOXYLATION · PDF fileundergo chemical reaction than the singlet...
162
(i SOIiE PHOTOINDUCED DECARBOXYLATION REACTIONS. A Thesis presented for the degree of Doctor of Philosophy in the Faculty of Science by PETER ROBERT STEINER Department of Chemistry, University of Leicester, September, 1971.
Transcript of SOIiE PHOTOINDUCED DECARBOXYLATION · PDF fileundergo chemical reaction than the singlet...
(i
SOIiE PHOTOINDUCED DECARBOXYLATION
REACTIONS.
A T h e s i s
p r e s e n t e d f o r th e d e g re e o f
D o c to r o f P h i lo s o p h y
i n th e
F a c u l t y o f S c ie n c e
by
PETER ROBERT STEINER
D e p ar tm en t o f C h e m is t ry ,
U n i v e r s i t y o f L e i c e s t e r ,
S ep tem ber , 1971 .
UMI Number: U378252
All rights reserved
INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted.
In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if material had to be removed,
a note will indicate the deletion.
Disscrrlation Publishing
UMI U378252Published by ProQuest LLC 2015. Copyright in the Dissertation held by the Author.
Microform Edition © ProQuest LLC.All rights reserved. This work is protected against
unauthorized copying under Title 17, United States Code.
ProQuest LLC 789 East Eisenhower Parkway
P.O. Box 1346 Ann Arbor, Ml 48106-1346
(iij
ACKNOWLEDGEMENTS
I w ish t o e x p r e s s my s i n c e r e g r a t i t u d e
t o D r. R, S , D av id so n f o r h i s h e lp and
en co u rag em en t d u r in g th e p e r i o d t h a t
t h i s work was u n d e r t a k e n ,
I a l s o w ish to th a n k Mrs, C. A,
C rane f o r th e t y p in g o f t h i s t h e s i s ,
th e S c ie n c e R e se a rc h C o u n c i l f o r a
m a in te n a n c e g r a n t , and my p a r e n t s f o r
t h e i r c o n t in u e d s u p p o r t .
(iii)
STATEMENT
The e x p e r im e n ta l work in t h i s t h e s i s has
been c a r r i e d o u t by th e a u th o r i n th e
D epartm ent o f C h em is try o f th e U n iv e r s i ty
o f L e i c e s t e r , be tw een O ctober 1968 and
Septem ber 1971. The work has n o t been
p r e s e n t e d , and i s n o t b e in g c u r r e n t l y
p r e s e n t e d f o r any o t h e r d e g re e .
Septem ber, 1971.
IIV)
Some o f th e work p r e s e n t e d i n t h i s t h e s i s h a s b e en p r e v i o u s l y
p u b l i s h e d a s fo l lo w s*
( i ) The P h o t o s e n s i t i s e d D e c a r b o x y la t io n o f C a r b o x y l i c
A c id s by B enzophenone a n d Q u in ones ;
R .S . D av id so n and P .R . S t e i n e r , J , Chem, Soc . (C ),
1682 , (1 9 7 1 ) .
( i l ) The P h o t o s e n s i t i s e d D e c a r b o x y la t io n o f C a r b o x y l ic
A c id s by A ro m a tic K e to n e s ;
R .S . D av id so n , K, H a r r i s o n , and P .R . S t e i n e r ,
J , Chem. Soc . (c) . I n p r e s s .
( i i i ) The Mechanism o f th e Benzophenone P h o t o s e n s i t i s e d
D e c a r b o x y la t io n o f C a r b o x y l i c A c id s ;
R .S . D av id so n and P .R . S t e i n e r , Chem. Comm., I n p r e s s .
(V)
A b s t r a c t
Some o f th e fu n d a m e n ta l a s p e c t s o f p h o to c h e m is try have
b e en d i s c u s s e d .
The p h o to in d u c e d d e c a r b o x y l a t i o n o f c a r b o x y l i c a c i d s and
c a r b o x y la te a n io n s is r e v ie w e d , a s w e l l a s d e c a r b o x y l a t i o n s
s e n s i t i s e d by s a l t s ( e . g . c e r iu m (IV ) s a l t s ) , h e t e r o c y c l i c
compounds ( e . g . a c r i d i n e ) , a n d c a r b o n y l compounds ( i . e .
b i a c e t y l ) . D e c a r b o x y la t io n s s e n s i t i s e d by ^ b io c h e m ic a l ly -
a c t iv e * m o le c u le s e . g . f l a v i n s , a r e a l s o re v ie w e d .
The p h o to in d u c e d d e c a r b o x y l a t i o n o f c a r b o x y l i c a c i d s
o f ty p e RXCH2 CO2 H (w here *R ̂ i s an a l k y l o r a r y l g ro u p ,
a n d *X* = 0 , S, o r NH) , s e n s i t i s e d by v a r i o u s k e to n e s and
q u in o n e s , h a s b e en s t u d i e d . Y ie ld s o f c a rb o n d io x id e
an d s u b s t i t u t e d h y d ro c a rb o n s , o f ty p e RXCH3 , have b e en o b ta in e d .
O th e r p r o d u c t s t u d i e s have shown t h a t w i th a few q u in o n es
e . g . t e t r a c h l o r o - p - b e n z o q u i n o n e , s t a b l e a d d u c t s a r e fo rm ed ,
w hereas a r o m a t i c k e to n e s g iv e t h e c o r r e s p o n d in g p i n a c o l s .
Q uenching s t u d i e s hav e b e e n c a r r i e d o u t t o d e te rm in e th e
r a t e c o n s t a n t s f o r d e c a r b o x y l a t i o n , and a k i n e t i c scheme i s
p ro p o s e d . E v id e n c e i n s u p p o r t o f a mechanism i n v o lv i n g an
e l e c t r o n t r a n s f e r , from t h e a c i d t o th e e x c i t e d c a r b o n y l
g ro u p , i s p r e s e n t e d .
The p h o to in d u c e d d e c a r b o x y l a t i o n o f c a r b o x y l i c a c i d s ,
s e n s i t i s e d by q u i n o x a l i n e s , h a s b e e n b r i e f l y c o n s i d e r e d .
(Vi)
Y ie ld s o f a n i s o l e from th e d e c a r b o x y l a t i o n o f p h e n o x y a c e t ic
a c i d , u n d e r n i t r o g e n , have b e e n o b t a i n e d ; o t h e r p r o d u c t s , f r o m
r e a c t i o n s c a r r i e d o u t i n t h e p r e s e n c e o f a i r , were a l s o
o b t a i n e d . P o s s i b l e r e a c t i o n m echanism s a r e c o n s id e r e d .
fvii)
To Mura and Dad.
(viii)
CONTENTS
C h a p te r 1 - INTRODUCTION 1
1 .1 Some B a s ic A s p e c ts o f P h o to c h e m is t r y . 2
( i ) E l e c t r o n i c T r a n s i t i o n s i n O rg a n ic M o le c u le s . 2
( i i ) Quenchers an d D e a c t i v a t i o n o f E x c i t e d S t a t e s . 5
( i i i ) Quantum Y i e l d s . 6
1 .2 A Review o f P h o t o d e c a r b o x y la t io n R e a c t i o n s o f
C a r b o x y l ic A c id s and C a r b o x y la te A n io n s . 8
1 .3 A Review o f P h o t o d e c a r b o x y la t io n R e a c t io n s
I n v o lv in g B io c h e m ic a l S y s tem s . 28
C h a p te r 2 - PHOTOINDUCED DECARBOXYLATION OF
CARBOXYLIC ACIDS SENSITISED BY
CARBONYL COMPOUNDS. k l
2 .1 R e s u l t s and D i s c u s s i o n . 48
2 . 1 . 1 P r e l im i n a r y P h o t o d e c a r b o x y la t io n S t u d i e s . 48
2 . 1 . 2 P ro d u c t S t u d i e s f o r R e a c t io n s I n v o l v in g
A ro m a tic K e to n e s . 51
2 . 1 . 3 P r o d u c t S t u d i e s f o r R e a c t io n s I n v o lv in g
Q u in o n es . 61
2 . 1 . 4 Summary o f P r o d u c t F o rm a tio n . 69
2 . 1 . 5 M e c h a n is t ic S t u d i e s . 70
(ix)
2 .2 E x p e r im e n ta l . 90
2 . 2 .1 I n s t r u m e n t a t i o n . 90
2 .2 .2 A n a ly s e s by Gas L iq u i d C hrom atography . 91
2 . 2 .3 P r e p a r a t i o n o f M a t e r i a l s . 93
2 . 2 . 4 D e te r m in a t io n o f C arbon D i o x i d e . 96
2 , 2 . 3 I r r a d i a t i o n P ro c e d u re s . 98
2 . 2 . 6 B la n k P h o t o l y s e s o f th e A c id s . 100
2 . 2 . 7 P r o d u c t S t u d i e s . 100
2 . 2 . 8 D e te r m in a t io n o f th e R a te C o n s t a n t s f o r
D e c a r b o x y la t io n , 108
2 .2 .9 A c t in o m e t r y . 123
C h a p te r 3 - PHOTOINDUCED DECARBOXYLATION OF
CARBOXYLIC ACIDS SENSITISED BY
QUINOXALINES. 128
3 .1 R e s u l t s a n d D i s c u s s io n , 129
3 .1 . 1 P r e l i m i n a r y D e c a r b o x y la t io n S t u d i e s , 129
3 . 1 . 2 P r o d u c t S t u d i e s , 130
3 . 1 . 3 The Mechanism o f D e c a r b o x y la t io n . 136
3 ,2 E x p e r im e n ta l 138
3 . 2 . 1 G e n e ra l D e t a i l s . 138
3 . 2 . 2 S t a r t i n g M a t e r i a l s 138
3 . 2 . 3 A n a ly s e s by Gas L iq u i d C hrom atog raphy . 139
3 . 2 . 4 P r o d u c t S t u d i e s . 139
REFERENCES 144
(X)
E r r a t a
On P ag es 109 t o 122 ,
^ / i s h o u ld be [BaCOs
^ [B aC O s]^
CHAPTER 1
INTRODUCTION
1 .1 Some B a s ic A s p e c ts o f P h o to c h e m is t r y .
( i ) E l e c t r o n i c T r a n s i t i o n s i n O rg a n ic M o le c u le s .
The e l e c t r o n i c t r a n s i t i o n s v;hich o c c u r i n o r g a n ic
m o le c u le s a r e w e l l i l l u s t r a t e d by r e f e r e n c e t o th e c a rb o n y l
chrom ophore . The m o le c u la r o r b i t a l d e s c r i p t i o n o f th e
c a rb o n y l g roup i s ( ^ q q ) ̂ ( ' " c o . These o r b i t a l s
can be s c h e m a t i c a l ly r e p r e s e n t e d a s f o l lo w s I
E n erg y L e v e ls T r a n s i t i o n s
À
I n c r e a s i n gE nergy
TT
n
rr
'M
&
&&
n , TT
A
TT.TT
(w here a re two p a i r e d e l e c t r o n s , a n d \ o r 'j a r e u n p a i r e d
e l e c t r o n s ) .
T h ere a r e two e l e c t r o n i c t r a n s i t i o n s w hich c an o c c u r i n
th e c a rb o n y l chrom aphore ; t h e s e a r e n , tt and ir, t r a n s i t
i o n s , by r e f e r e n c e t o th e p ro m o tio n o f e l e c t r o n s a s d e p i c t e d
a b o v e . The fo rm e r t r a n s i t i o n i n v o lv e s t h e p ro m o t io n o f a
n o n -b o n d in g e l e c t r o n ^ , on oxygen, t o a ir a n t i b o n d i n g
o r b i t a l ; t h i s g iv e s r i s e t o a v i b r a t i o n a l l y e x c i t e d s i n g l e t
s t a t e w h ich , i n s o l u t i o n , l o s e s i t s e x c e s s v i b r a t i o n a l
e n e rg y t o th e s u r r o u n d in g m o le c u le s , t o g iv e th e l o w e s t
v i b r a t i o n a l s i n g l e t s t a t e . The tt, tt^ t r a n s i t i o n i n v o lv e s
th e p ro m o tio n o f an e l e c t r o n i n a ir o r b i t a l t o t h e o r b i t a l ,
to g iv e th e e x c i t e d s i n g l e t s t a t e , i n a n a n a lo g o u s m anner.
I n m ost c a rb o n y l compounds, and m ost n i t r o g e n h e t e r o c y c l i c s ,
th e t r a n s i t i o n s o f l o w e s t e n e rg y a r e c o n s i d e r e d t o be n , tt *
i n c o n f i g u r a t i o n .
The e x c i t e d s i n g l e t s t a t e c a n l o s e i t s e n e rg y by a
r a d i a t i o n l e s s t r a n s i t i o n , known a s **i n t e r n a l c o n v e rs io n * *,
t o g iv e th e s i n g l e t g ro u n d s t a t e ; i t can a l s o l o s e e n e rg y by
e m is s io n o f l i g h t , a p r o c e s s known a s **f l u o r e s c e n c e * * when
th e t r a n s i t i o n i s b e tw ee n s t a t e s o f l i k e m u l t i p l i c i t y . S p in
i n v e r s i o n o f a n u n p a i r e d e l e c t r o n , t o g iv e th e f i r s t e x c i t e d
t r i p l e t s t a t e , c a n a l s o o c c u r ; t h i s i s known a s **i n t e r s y s t e m
c ro s s in g * *,
The t r i p l e t s t a t e , r e s u l t i n g from i n t e r s y s t e m c r o s s i n g ,
l o s e s i t s e x c e s s v i b r a t i o n a l e n e r g y , i n a n a n a lo g o u s m anner
t o th e s i n g l e t , t o g iv e th e lo w e s t v i b r a t i o n a l t r i p l e t s t a t e .
T h is can t h e n l o s e i t s e n e r g y , t o g iv e th e s i n g l e t g ro u n d
s t a t e , e i t h e r by a r a d i a t i o n l e s s t r a n s i t i o n o r by e m is s io n
o f l i g h t ; th e l a t t e r p r o c e s s i s known a s **p h o s p h o r e s c e n c e **,
b e in g a t r a n s i t i o n b e tw ee n s t a t e s o f d i f f e r e n t m u l t i p l i c i t y .
Decay o f th e t r i p l e t s t a t e t o th e s i n g l e t g ro u n d s t a t e i s
r e l a t i v e l y s lo w , a s i t i s s p i n f o r b i d d e n . H ence , th e r a t e
o f f l u o r e s c e n c e e m is s io n i s f a s t e r t h a n th e r a t e o f p h o sp h
o re s c e n c e e m i s s io n . A ls o th e t r i p l e t s t a t e i s more l i k e l y t o
u n d e rg o c h e m ic a l r e a c t i o n th a n t h e s i n g l e t s t a t e , i f i n t e r
sy s tem c r o s s i n g o c c u r s e f f i c i e n t l y . I n m ost a r o m a t i c
k e to n e s i n t e r s y s t e m c r o s s i n g i s e x t r e m e ly e f f i c i e n t so t h a t
th e p h o to c h e m is t r y o f t h e s e compounds i s d o m in a te d by th e
f i r s t e x c i t e d t r i p l e t s t a t e .
The p r o c e s s e s d e s c r i b e d above a r e i l l u s t r a t e d i n th e
f o l lo w in g J a b l o n s k i d iagram ?
v i b r a t i o n a l s t a t e s
i n t e r s y s t e mc r o s s i n g
f l u o r e s c e n c e o f i n t e r n a l c o n v e r s io n
e x c i t a t i o n
p h o sp h o re sc e n c e
o f r a d i a t i o n l e s s
t r a n s i t i o n
v i b r a t i o n a l s t a t e s
The e n e r g i e s (E^) o f th e l o w e s t t r i p l e t s t a t e s (T^ ) o f
s e v e r a l k e to n e s a r e g iv e n i n th e f o l l o w i n g t a b l e I
C a rb o n y l Compound (kca l,/m o3e)
2X anthone 7 4 .2
2A ce to phenon e 7 3 ,6
2Benz ophe none 68 .5
2FTuorenone 5 3 .3
29 . 1 0 -A n th ra q u in o n e 6 2 .4
39 . 1 0 -P h e n a n th ra qu inon e 4 8 .8
2 -A c e ty ln a p h th 8 le n e * 5 8 ,0
( i i ) Q uenchers and D e a c t i v a t i o n o f E x c i t e d S t a t e s
C o n s id e r a m o le c u le o f b en zo p h e n o n e , i n i t s l o w e s t
e x c i t e d t r i p l e t s t a t e , T ^ , I t can l o s e i t s e n e rg y by th e
p r o c e s s e s d e s c r i b e d e a r l i e r . I t can a l s o be d e a c t i v a t e d by
c h e m ic a l r e a c t i o n s , one o f th e m ost common o f w hich i s
h y d ro g e n a b s t r a c t i o n from a l c o h o l s . T h is was f i r s t r e p o r t e d
by C ia m ic ia n a n d S i l b e r ^ %
[PhgCO]^^ + RgCHOH PhgCOH + RgCOH
The benzophenone t r i p l e t (E^=68 , 5 k c a l . / m o l e ) can a l s o be
d e a c t i v a t e d by t r a n s f e r o f e n e rg y t o a n o t h e r m o le c u le , w hich
h a s a lo w e r t r i p l e t e n e rg y e . g . n a p h th a le n e (Erp = 6 0 ,9 k c a l , /
m o le ) ̂ , T h i s p r o c e s s i s known a s **q u e n c h in g * * o f th e
e x c i t e d s t a t e , th e benzophenone b e in g named th e * 'donor** o r
* *s e n s i t i s e r * *, an d th e n a p h th a le n e th e * ' a c c e p t o r * * o r
**q u e n c h e r* * ( i n t h i s p r o c e s s ) . The benzophenone t r i p l e t
i s v e ry e f f i c i e n t l y quenched by n a p h th a le n e and i s d e a c t i v a t e d
t o th e s i n g l e t g ro u n d s t a t e ; th e n a p h th a le n e i s e x c i t e d to
th e f i r s t e x c i t e d t r i p l e t s t a t e , Moore and Ketchum® have
sho\m t h a t th e r a t e o f q u e n ch in g by n a p h th a le n e i s d i f f u s i o n -
c o n t r o l l e d , Oxygen i s a l s o a d i f f u s i o n - c o n t r o l l e d q u en ch e r
f o r t h e b enzophenone t r i p l e t ^ ,
Q uench ing o f e x c i t e d s t a t e s i s a v e ry u s e f u l t o o l to th e
p h o to c h e m is t and can be u s e d t o d e te rm in e a b s o l u t e r a t e s o f
p h o to c h e m ic a l r e a c t i o n s *
( i i i ) Quantum Y i e ld s
The quantum y i e l d o f a p h o to c h e m ic a l p r o c e s s g iv e s a
m easu re o f th e e f f i c i e n c y o f t h a t p r o c e s s . C o n s id e r th e
f o l l o w i n g r e a c t i o n s !
M + h^ A + B
A -> X
(w here **A** an d **B*' a r e s t a b l e m o le c u le s o r r e a c t i v e
m o le c u la r f r a g m e n ts fo rm ed a s th e im m edia te e f f e c t o f l i g h t
a b s o r p t i o n by M, and **X** i s a s t a b l e p r o d u c t ) .
The quantum y i e l d , <|)^, o f f o r m a t io n o f A i s d e f i n e d
a s .
d[A] No. o f m o le c u le s , r a d i c a l s , o r I o n s o f
JL _ d t _ A fo rm e d /c m ^ -s e c .YA ■ ---------------- ■ -------------------------------------------------
No, o f q u a n ta a b s o rb e d by M /cm ^-sec .
T h is i s known a s th e * 'p r im a r y quantum y i e l d ' ' , a s t h e e n t i t y
A i s fo rm ed i n th e p r im a r y p h o to c h e m ic a l s t e p . I n p r a c t i c e
i t i s e a s i e r t o m easu re th e f o r m a t io n o f th e s t a b l e p r o d u c t ,
X, The ' ' o v e r a l l quantum y i e l d ' ' , s i m i l a r l y
d e f i n e d a s %
d[x]
d t No. o f m o le c u le s X fo rm e d /c m ^ -s e c .
l a b s No. o f q u an ta a b s o rb e d by M /cm ^-sec .
gF o r b en zo p h en o n e , i n t e r s y s t e m c r o s s i n g i s v e ry e f f i c i e n t
i . e . ÿ Ti ^ where ^ i s th e o v e r a l l quantum y i e l d
f o r f o r m a t io n o f th e t r i p l e t s t a t e , i . e . e a c h quantum o f
l i g h t a b s o r b e d g iv e s a m o lecu le o f benzophenone i n i t s
t r i p l e t s t a t e .
f
8
1 .2 A Review o f P h o to d e c a r b o x y la t io n Rea c t i o n s o f C a r b o x y l i c
A c id s a n d Car b o x y la t e A n ions
P r e f a c e
I n t h e f o l lo w in g s e c t i o n , p h o to d e c a r b o x y l a t i o n r e a c t i o n s
o f c a r b o x y l i c a c i d s a n d c a r b o x y l a t e a n io n s a r e re v ie w e d .
The re v ie w i s p r e s e n t e d a s a f a c t u a l a c c o u n t a n d n o t a s a
c r i t i c a l d i s c u s s i o n . R e a c t io n s i n v o l v i n g b io c h e m ic a l
sy s te m s a r e re v ie w e d i n S e c t i o n 1 . 3 .
R e a c t io n s I n v o l v in g C a r b o x y la te A n io n s
gJ o s c h e k an d G ro s s w e in e r s t u d i e d th e e f f e c t o f i r r a d i a t
i n g aq ueous s o l u t i o n s o f t h e a n io n s o f p h e n y l a c e t i c a c i d and
p h e n o x y a c e t ic a c i d . U s in g f l a s h p h o t o l y s i s t e c h n iq u e s th e y
showed t h a t e l e c t r o n e j e c t i o n o c c u r r e d from th e a n io n t o g iv e
r a d i c a l s !
PhCHgCQg ----- -------y PhCHgCOs — > PhCfig + COg
^ . .PhOCHg COg PhOCHg COg —> PhOCHg + COg
(where * * €: * * i s a s o l v a t e d e l e c t r o n ) .
C ro sby a n d Tang^® fo u n d t h a t , n a p h t h y l a c e t a t e io n s a l s o
d ec a r b o x y l a t e d on i r r a d i a t i o n i n aq ueou s s o l u t i o n g iv in g
1 - m e th y ln a p h th a l e n e ( I ) a s t h e p r im a ry p r o d u c t , i n th e a b se n c e
o f oxygen . When oxygen was p r e s e n t , l - n a p h t h y l m e t h a n o l ( I l )
and 1- n a p h t h a l d e h y d e ( I I I ) were among th e p r o d u c t s fo rm ed .
They s u g g e s t e d t h a t th e p r o d u c t I c o u ld be fo rm ed by e i t h e r
an i o n i c mechanism (pa thw ay [ i ] ) o r a f r e e r a d i c a l m echanism
(pathw ay [1 1 ] ) ;CH, CH
OCH,CO,
CHz
They p r e f e r r e d th e r a d i c a l p a th w a y , [ i i ] , f o r t h e
f o l lo w in g r e a s o n s . Under n i t r o g e n t h e f o r m a t io n o f I was
p H - in d e p e n d e n t ; t h i s would be e x p e c te d f o r [ i i ] , b u t [ i ]
s h o u ld be p H -d e p e n d e n t , A l s o , t h e p r o d u c t i o n o f t h e
o x y g e n a te d p r o d u c t s c o u ld be e a s i l y e x p l a i n e d on th e b a s i s
o f r e a c t i o n o f l a w i th o x y g e n , a s i n [ i i i ] . I n t h e
a b se n c e o f ox ygen , h y d ro g en a to m s , fo rm ed by r e a c t i o n o f12h y d r a t e d e l e c t r o n s w i th w a te r ( e q u a t i o n l ) ^ c o u l d combine
w i th l a t o g iv e i ;
€ + HgO H* + OH (1)
D e c a r b o x y la t io n o f c a r b o x y l a t e a n io n s was a l s o o b s e rv e d13
by Marge rum a n d P e t r u s i s , who i r r a d i a t e d aq u eo u s s o l u t i o n s
o f n i t r o p h e n y l a c e t a t e i o n s ;
CH.
OgN 0«N
CO,
10
D e c a r b o x y la t io n was n o t o b s e rv e d from th e u n d i s s o c i a t e d a c i d .
The quantum y i e l d f o r d e s t r u c t i o n o f 3 ~ n i t r o p h e n y l a c e t a t e ,
/ ^ . - n i t r o p h e n y l a c e t a t e , and 4 - n i t r o h o m o p h t h a l a t e were a p p ro x
i m a te ly 0 . 6 , w h e rea s p h e n y l a c e t a t e d e c a r b o x y l a t i o n o c c u r r e d14w i th a quantum y i e l d o f o n ly 0 .0 1 , s u g g e s t i n g t h a t
d i f f e r e n t m echanism s were o p e r a t i v e . They s u g g e s te d t h a t th e
c a rb o n d io x id e was e v o lv e d i n a o n e - s t e p p r o c e s s d i r e c t l y
from th e e x c i t e d s t a t e o f th e a n io n , h a v in g fo u n d no e v id e n c e9
f o r t h e i n te r m e d ia c y o f s o l v a t e d e l e c t r o n s . From f l a s h
p h o t o l y s i s s t u d i e s 4 - n i t r o h o m o p h t h a l a t e , 2- , an d 4 - n i t r o -
p h e n y l a c e t a t e i o n s were fo u n d t o g iv e ' ' a c i - n i t r o ' *
i n t e r m e d ia t e s (TV)I
e . g .
M o T
The a b s o r p t i o n maximum o f th e t r a n s i e n t from 2 - n i t r o p h e n y l -
a c e t a t e i o n s was th e same a s t h e 2- n i t r o b e n z y l a n io n t r a n s i e n t
o b s e rv e d from p h o t o l y s i s o f 2- n i t r o t o l u e n e i n a q u eo u s b a s e ;
a l s o , t h e r a t e o f d ecay o f t h e s e i n t e r m e d i a t e s i n 0 .1 N NaOH
was th e sam e. 3 - N i t r o p h e n y l a c e t a t e i o n s , how ever, d i d n o t
g iv e an a c i - i n t e r m e d i a t e , t h i s b e in g c o n s i s t e n t w i th th e
p ro p o s e d m echanism s in c e th e 3 - n i t r o b e n z y l a n io n w ould n o t
be r e s o n a n c e s t a b i l i s e d and th u s w ould be e x p e c te d t o behave
a s a s h o r t - l i v e d c a r b a n i o n . As th e quantum y i e l d s were
co m parab le f o r t h e 3- and 4 - n i t rophe n y l a ce t a t e i o n s , th e
f o r m a t io n o f a m e t a s t a b l e a c i a n io n was n o t e s s e n t i a l t o th e
d e c a r b o x y l a t i o n p r o c e s s . These quantum y i e l d s , how ever,
d i d n o t f i t t h e m echanism o f Zimmerman i n w hich t h e e x c i t e d
CH.
11
S ta te o f a m -n itro s tr u c tu r e i s c o n s id e r e d to be fa v o u r a b le ,
and th a t o f a p - n i t r o u n fa v o u r a b le , f o r h e t e r o l y t i c c le a v a g e .
R e a c t io n s I n v o l v i n g N itro -A m in o A c id s
D u r in g i n v e s t i g a t i o n s i n t o th e s e p a r a t i o n o f d i n i t r o -
p h e n y la m in o a c i d s , by c h ro m a to g ra p h y , B l a c k b u r n o b s e r v e d
t h a t d e c o m p o s i t io n o f t h e s e a c i d s o c c u r r e d on t h e co lum ns i n18
s u n l i g h t . T h is was a l s o o b s e rv e d by M i l l s . Among t h e
p r o d u c t s i s o l a t e d from i r r a d i a t i o n o f n i t r o - a m i n o a c i d s , i n19
mildly a l k a l i n e s o l u t i o n , were N - a l k y l d i n i t r o a n i l i n e s and, ao 21,2.%4 - n i t r o - 2 - n i t r o s o a n i l i n e s . R u s s e l l fo u n d t h a t
p h o t o l y s i s o f N - 2 ,4 - d i n i t r o p h e n y l - N - m e th y l l e u c in e i n mildly
a l k a l i n e s o l u t i o n gave p -m e th y lb u t y r a ld e h y d e and N -m e th y l-23
4 - n i t r o - 2 - n i t r o s o a n i l i n e ; how ever, P o l l i t t i s o l a t e d
5- n i t r o b e n z i r a i d a z o l e 3 - o x id e i n good y i e l d from p h o t o l y s i s
o f a n a q u eo u s s o l u t i o n o f N -2 , 4 - d i n i t r o p h e n y l g l y c i n e i n th e24
pH ra n g e 2 - 5 . N e ad le a n d P o l l i t t fo u n d t h a t y i e l d s o f
th e s u b s t i t u t e d b e n z im id a z o le p r o d u c t , from t h e s e r e a c t i o n s ,
v a r i e d w i th pH i n a n u n u s u a l l y c o m p l ic a te d manner, and
s u g g e s t e d t h a t t h e r e were s e v e r a l a l t e r n a t i v e p H -d e p en d e n t
p a th w a y s t o a c c o u n t f o r t h i s c o m p le x i ty . I n a l a t e r p a p e r^ ^
th e y r e p o r t e d f u r t h e r i n v e s t i g a t i o n s c o n c e r n in g th e d e c a rb o x y
l a t i o n o f t h e s e a c i d s . They fo u n d t h a t th e p r o d u c t s were
c a rb o n d i o x i d e , U - n i t r o - 2- n i t r o s o a n i l i n e , an a ld e h y d e w i th
one l e s s c a rb o n atom t h a n t h e p a r e n t amino a c i d , an d a
s u b s t i t u t e d 6- n i t r o b e n z i m i d a z o l e 1 - o x i d e . The r e a c t i o n s
w ere m ost e f f i c i e n t a t pH < 3 , s u g g e s t i n g t h e im p o r ta n c e o f
th e u n d i s s o c i a t e d a c i d t o th e r e a c t i o n m echanism . The
12
m echanism th e y p o s t u l a t e d in v o lv e d a c o n c e r t e d d e c a r b o x y la
t i o n and oxygen t r a n s f e r , a s th e i n i t i a l s t e p , g i v i n g th e
i n t e r m e d i a t e V. T h is c o u ld c o l l a p s e by p a th w ay s [ i ] , [ i i ] ,
o r [ i i i ] t o g iv e th e p r o d u c t s ,w h ich were fo rm ed i n v a r y in g
p r o p o r t i o n s d e p e n d e n t on th e pH o f th e s o l u t i o n and s t r u c t u r e
o f th e d i n i t r o a m i n o a c i d i n v e s t i g a t e d !
nrIcrWcOjH
NO.
NOg
NHR n r ’.c r V o h
NOM - R R C O
n r '.c r V
( R i , R̂ , R° a r e a l k y l g ro u p s o r h y d ro g e n e x c e p t where i n d i c a t e d ) .
13
aaAn a l t e r n a t i v e mechanism was l a t e r p ro p o s e d by M eth-Cohn*
T h is a l s o i n v o lv e d an oxygen t r a n s f e r b u t t h i s d i d n o t o c c u r
w i th th e c o n c e r t e d l o s s o f c a rb o n d io x id e %
RV.C.COgH
r ’.N î '^ O
N+
CRR'.N
W
NHR
f̂ .fPc o
NO
OH
NO. NO.
R:N
NOg NOo
R.NCR̂ .R̂ OH
NO
NOg
T h is m echanism a c c o u n te d f o r t h e r e a c t i o n b e in g a c i d c a t a l y s e d
and t h e f a c t t h a t t h e r a t e o f r e a c t i o n , a s m easu red by c a rb o n
d i o x id e e v o l u t i o n , was v e ry s i m i l a r f o r a ra n g e o f 2 , 4 -
d in i t r o p h e n y l a m i n o a c i d s .
14
3.7M cParlane and R u s s e l l i n v e s t i g a t e d t h e h e c e s s i t y of*
a n i t r o g roup o r th o t o th e am ino a c i d r e s i d u e by p h o t o l y s i n g
p - n i t r o p h e n y l v a l i n e ; o b v io u s ly w i th t h i s compound no i n t r a
m o le c u la r oxygen t r a n s f e r c o u ld o c c u r . They fo u n d t h a t on
i r r a d i a t i o n i n a q u eo u s s o l u t i o n (pH 6 .0 ) r a p i d s im p le
d e c a r b o x y l a t i o n o c c u r r e d !
CH(iPr).C02HNH N H .(\B u.)
-CO^
NOg
T h is d e m o n s t r a te d t h a t an o r t h o - n i t r o g roup was n o t a
m e c h a n i s t i c n e c e s s i t y ^ a s p r o p o s e d by M eth-Cohn ^ an d t h a t
d e c a r b o x y l a t i o n may be t h e p r im a ry m e c h a n i s t i c s t e p , a s
p r e v i o u s l y s u g g e s te d
28I t was fo u n d t h a t an a n a lo g o u s d e c a r b o x y l a t i o n r e a c t i o n
e x i s t e d w i th o - n i t r o p h e n o x y a c e t i c a c i d s w hich y i e l d e d
0 - n i t r o s o p h e n o l s on i r r a d i a t i o n i n a q u eo u s s o l u t i o n .
a - ( 2 , 4 - D in i t r o p h e n o x y ) p r o p i o n i c a c i d gave c a rb o n d io x id e ,
4 - n i t r o - 2 - n i tP O s q p h e n o l , a n d a c e ta ld e h y d e o v e r t h e pH ra n g e
1 - 1 2 . H ence , i n i t s p H -in d ep e n d en c e th e r e a c t i o n d i f f e r e d
from th e p h o t o l y s i s o f th e amino ac ids^^ ' A mechanism
f o r t h e r e a c t i o n was n o t p ro p o s e d .
R e a c t i o n s I n v o l v in g S a l t s o f A c id s
39I t was fo u n d t h a t some a l i p h a t i c c a r b o x y l i c a c i d s
c o u ld be d e c a r b o x y l a t e d by i r r a d i a t i o n o f t h e i r c e r iu m ( lV )
15
s a l t s w i th t h e a c i d a s th e s o l v e n t e . g . c e r i u m ( I V ) - a c e t a t e i n
a c e t i c a c i d . The mechanism p r o p o s e d in v o lv e d t h e d i r e c t
fo rm a t io n , from t h e e x c i t e d s a l t , o f a c y lo x y r a d i c a l s , w hich
f ra g m e n te d r a p i d l y t o g iv e c a rb o n d i o x i d e . The a l k y l
r a d i c a l s (R ) so p ro d u c e d were o x i d i s e d t o carb on ium io n s
(R* ) , which gave a lk e n e s and e s t e r s a s p r o d u c t s !
TV ^ TTT *Ce-^^'OgCB 35QQ° + RCOa ( 2 )
RCO3 " » . R* + CQa
r ’ + C e ^ -------3. R* +
The r a t e o f d e c a r b o x y l a t i o n was in d e p e n d e n t o f t h e a l k y l
m o ie ty , th e r a t e - d e t e r m i n i n g s t e p b e in g g iv e n i n e q u a t i o n ( 2 ) .
A lk a n e s w ere a l s o fo u n d t o b e r e a c t i o n p r o d u c t s ; t h e s e were
fo rm ed from th e a l k y l r a d i c a l s (R ) by h y d ro g en a b s t r a c t i o n
and d i m é r i s a t i o n r e a c t i o n s . The f o r m a t io n o f a l k y l r a d i c a l s
a s p r im a ry i n t e r m e d i a t e s i n th e r e a c t i o n was d e m o n s t r a te d by
a d d i t i o n o f h y d ro g e n d o n o rs e . g . i n th e p h o t o l y s i s o f
c e r iu m (I"V)-butyrat e a d d i t i o n o f c h lo ro fo rm t o th e r e a c t i o n
m ix tu re g r e a t l y e n h a n c e d th e y i e l d o f p ro p a n e !
TV •CHsCHgCHgCOs Ce ---------- t t T ^ CH3 CE3GH3
-Ce^
GHGI3GH3GH2GH3 ^ GH3GH3GH3 + GGI3
Quantum y i e l d s f o r t h e r e a c t i o n s were a p p ro x im a te ly u n i t y ,30K ochi an d B e th e a e x te n d e d t h i s ty p e o f r e a c t i o n t o
16
t h a l l iu m s a l t s o f c a r b o x y l ic a c i d s , e . g . a c e t i c , n - v a l e r i c ,
p h e n y la c e t i c , c y c l o p e n t y l a c e t i c , e t c . . They s u g g e s te d t h a t
r e a c t i o n p ro c e e d e d v ia a r a d i c a l m echanism , a s f o l lo w s !
TTT TT •(RCQa (RCOa ) s T l + R + COg
TT f a s t T •(RCO3 ^ RCOaTl-^ + R + CO3
oWhen i r r a d i a t i o n was c a r r i e d o u t a t 2537A, th e p r o d u c t from
d im é r i s a t i o n o f th e a lk y l r a d i c a l s (R ) was fo rm ed i n f a i r l y
h ig h y i e l d e . g . 33% o c ta n e i n th e p h o t o ly s i s o f n - v a l e r i c 0
a c id a t 2537A. They s u g g e s te d t h a t u n d e r th e s e p h o t o ly s i s
c o n d i t i o n s , th e a l k y l r a d i c a l s w ere d e r iv e d from h o m o ly s is
o f th e same t h a l l iu m ( I I I ) s p e c i e s ; u n d e r th e s e c ir c u m s ta n c e s
two a l k y l r a d i c a l s w ould b e fo rm ed i n c lo s e p ro x im i ty and
th e d i m é r i s a t i o n w ould be f a i r l y e f f i c i e n t .
0P h o t o l y s i s a t 3500A g e n e r a te d a lk a n e s a s th e m ain
p r o d u c t e . g . 69% b u ta n e an d 7% o c ta n e from p h o t o l y s i s o f. 0
n - v a l e r i c a c i d c . f . 31% b u ta n e when p h o to ly s e d a t 2537A.
U s in g th e lo n g e r w a v e le n g th i r r a d i a t i o n th e t h a l l i u m ( I l )
in te r m e d ia te w ould be p ro d u c e d i n a l e s s e n e r g e t i c s t a t e0
th a n t h a t p ro d u c e d a t 2537A ,and h en ce th e fo rm e r s p e c ie s w i l l
f ra g m e n t s u f f i c i e n t l y s lo w ly to re d u c e th e in c id e n c e o f
r a d i c a l d i m é r i s a t i o n . O x id a tio n o f a lk y l r a d i c a l s (R ) by
t h a l l i u m ( l l l ) o c c u r r e d g iv in g carbon ium io n s w hich l e d t o
a lk e n e s and e s t e r s ( a s f o r c e r iu m (IV ) ,
31K ochi e t a l o b se rv e d t h a t p h o to d e c a r b o x y la t io n o f
17
c a r b o x y l ic a c id s c o u ld a l s o b e e f f e c t e d from t h e i r l e a d ( lV )
s a l t s . They p o s t u l a t e d t h a t a r a d i c a l c h a in m echanism
in v o lv in g th e f o l lo w in g p r o p a g a t io n s t e p s was o c c u r r in g !
ECQaPb^^^ - » R* + CO3 + ( 3 )
R* + RGOgPb^^ i P + RCpaPb^^^ ( k )
They s u g g e s te d t h a t m u ltib o n d c le a v a g e o c c u r r e d to g iv e
c a rb o n d io x id e and a l k y l r a d i c a l s ; h e n c e , p a r t o f th e d r i v in g
f o r c e f o r th e p r o c e s s was d e r iv e d from th e fo rm a t io n o f
c a rb o n d io x id e . They fo und t h a t th e r a t e o f d e c a r b o x y la t io n
was v e ry d e p e n d e n t on th e s t r u c t u r e o f th e a l k y l m o ie ty o f th e
a c i d , i n th e m anner t e r t i a r y ^ se c o n d a ry ), p r im a ry ( e , g , p i v a l i c
a c i d ) i s o b u t y r i c a c i c ^ n - b u ty r i c a c i d ) . They s u g g e s te d t h a t
t h i s was l a r g e l y due t o th e p ro p a g a t io n s t e p k b e in g more
f a v o u ra b le f o r t e r t i a r y th a n p r im a ry a c i d s , due to th e fo rm
a t i o n o f a more s t a b l e carbon ium io n . The p r o d u c ts o f r e a c t i
on v/ere a lk a n e s ,a s f o r th e c e riu m and th a l l iu m c a s e s , ( d e r iv e d
from a lk y l r a d i c a l s , R , by d im é r i s a t i o n a n d h y d ro g en a b s t r a c
t i o n , m a in ly from th e a - p o s i t i o n o f th e c a r b o x y l ic a c id ) , and
a lk e n e s and e s t e r s ( d e r iv e d from carbon ium i o n s , R* ) , The
m ain d i f f e r e n c e b e tw ee n th e r e a c t i o n s w ith ce riu m s a l t s an d
l e a d s a l t s was t h a t i n th e fo rm e r c a se th e l i g h t e n e rg y was
s u f f i c i e n t t o hom olyse th e c e r iu m ( IV ) - c a rb o x y la te bonds
d i r e c t l y to a c y lo x y r a d i c a l s , w hereas i n th e l a t t e r c a se th e
a d d i t i o n a l d r i v in g f o r c e from c a rb o n d io x id e fo rm a t io n was
n e c e s s a r y .
18
R e a c tio n s I n v o lv in g H e te r o c y c l ic Compounds
33lN o y o rl e t a l fo u n d t h a t c a r b o x y l ic a c id s w ere
d e c a rb o x y la te d when p h o to ly s e d In th e p re s e n c e o f c e r t a i n
b e n z o p y r ld ln e s , e . g . a c r l d l n e . The a lk y l o r a r y l r a d i c a l so
p ro d u c e d fo rm ed an a d d i t i o n compound (V I) w ith th e re d u c e d
a c r l d l n e u n ltZ
H
-G O ,
VI
RCOgH +
R = Me, t -B u , PhCHg, e t c .
They a l s o fo u n d t h a t th e r e a c t i o n c o u ld o c c u r In tra m o le c u la r ly %
e . g .
(CH2) 5C02H
-CO,
H
Q u in o lin e an d I s o q u ln o l ln e w ere a l s o e f f e c t i v e i n b r i n g in g
a b o u t d e c a r b o x y la t io n ; w ith q u in o l in e , a l k y l a t i o n o c c u r re d
a t th e 2 - an d 4 - p o s i t i o n s . On th e b a s i s t h a t p l v a l l c a c i d
c o u ld b e d e c a rb o x y la te d , a m echanism I n v o lv in g th e I n i t i a l
a b s t r a c t i o n o f a n a -h y d ro g e n atom from th e c a r b o x y l ic a c i d ,33a s h ad b e e n s u g g e s te d f o r a s i m i l a r r e a c t i o n , was d i s c o u n te d .
The m echanism was I n t e r p r e t e d I n te rm s o f a c id - b a s e e q u i l i b r i a .
A c r ld ln e I n I t s g ro u n d s t a t e was known t o be a weak b a se 34
(pKa 5 . 5 ) , b u t showed a m arked enhancem en t o f b a s i c i t y i n
th e f i r s t e x c i t e d s i n g l e t s t a t e (pKa 1 0 .6 ) .O n i r r a d i a t i o n .
19
t h e r e f o r e , th e a c r l d l n e , p ro b a b ly i n I t s s i n g l e t s t a t e ,
c a p tu r e d th e -OH p r o to n from th e c a r b o x y l ic a c i d and fo rm ed
a n e x c i t e d com plex o f a c r id in iu m an d c a r b o x y la te i o n s , V I I .
S u b se q u e n t d e c a r b o x y la t io n p ro d u c e d an io n p a i r , V I I I , whose
c o m b in a tio n gave th e p r o d u c t , V II
RCO2H
V\
J 3- C - R ^ II
O
—COo
Vi\
v u \
The a u th o r s c o n s id e r e d a n a l t e r n a t i v e m e c h a n ism ,in v o lv in g
r a d ic a l s ,w h e r e b y p r o to n t r a n s f e r was fo l lo w e d by e l e c t r o n
t r a n s f e r from th e c a r b o x y la te io n to th e a c r id in iu m io n ; th e
a c y lo x y r a d i c a l s g e n e r a te d w ould l o s e c a rb o n d io x id e an d
c o m b in a tio n o f th e r a d i c a l s ,p r o d u c e d w i th in a s o lv e n t c a g ^
w ould g iv e th e p r o d u c t . H ow ever, on u s in g p ,p - d ip h e n y l -
p r o p io n ic a c id th e a d d u c t IX was th e o n ly p r o d u c t i s o l a t e d ;
th e r e was no t r a c e o f a d d u c t X ,w hich w ou ld have r e s u l t e d
from th e e x p e c te d p h e n y l m ig r a t io n i f a p ,p -d ip h e n y lm e th y l35
r a d i c a l was in v o lv e d #
20
+ (^gCHCHgCOgH
H CH|(|>)CH24>
H
X IX
The r e s u l t s c o u ld be i n t e r p r e t e d by a ssu m in g a n in tim a te * *
r a d i c a l p a i r o r v e ry f a s t r a d i c a l c o m b in a tio n . The r e a c t i o n s
w ith q u in o l in e and i s o q u i n o l i n e p ro b a b ly p ro c e e d e d v i a a
s i m i l a r m echanism ,
^ n in t r a m o le c u la r d e c a r b o x y la t io n r e a c t i o n , in v o lv in g36th e p y r id in e n u c le u s ,w a s d is c o v e re d by S te r m i tz and H uang,
They fo u n d t h a t i r r a d i a t i o n o f aqueous s o l u t i o n s o f 2 - , 3 - ,
an d 4 - p y r i d y l a c e t i c a c id s y i e l d e d th e c o r re s p o n d in g 2- , 3 - ,
and U -m e th y Ip y r id in e s and c a rb o n d io x id e . The i n i t i a l r a t e
o f d e c a rb o x y la t io n was a maximum a t pH 4 . 0 ; a t h ig h e r o r
lo w e r pH v a lu e s th e p h o to r e a c t io n s lo w ed c o n s id e r a b ly ,
s u g g e s t in g t h a t e i t h e r XI o r X II was th e g ro u n d s t a t e s p e c ie s
in v o lv e d ;
H
CHgCOgH
XI XII
21
They s u g g e s te d t h a t l o s s of* c a rb o n d io x id e o c c u r r e d from th e
e x c i t e d s t a t e o f s p e c ie s X I.
An i n t r a m o l e c u l a r p h o to d e c a r b o x y la t io n r e a c t i o n ,
in v o lv in g th e p y r im id in e n u c le u s , was d is c o v e re d by Wang,37
N n a d i, a n d G r e e n fe ld , They fo u n d t h a t i r r a d i a t i o n o f
a q u eo u s s o l u t i o n s o f t h y m i n e - l - a c e t i c a c i d ( X I I I ) and
u r a c i l - l - a c e t i c a c i d (XIV) r e s u l t e d i n d e c a r b o x y la t io n , th e
u r a c i l d e r i v a t i v e g iv in g a h y d ra te d p ro d u c tI
p H 3'2
XIIIKO
0
ICHgCOgH
CHH N
CH3
p H 3*1
XIV
0
H N H N
OH
CH3
The th y m in e d e r i v a t i v e p ro b a b ly a l s o fo rm ed a h y d ra te d38
p r o d u c t , b u t was to o u n s t a b le to be i s o l a t e d . They n o te d
t h a t th e c o r r e s p o n d in g p r o p io n ic a c i d d e r i v a t i v e s e . g .
th y m in e - 1 - p r o p i o n ic a c i d , d id n o t p h o to d e c a rb o x y la t e .
39I n a l a t e r p a p e r th e y s t u d i e d th e s e r e a c t i o n s
f u r t h e r an d s u g g e s te d t h a t an in te r m e d ia te s p e c ie s was
i n v o lv e d ; t h i s was e i t h e r a v i b r a t i o n a l l y e x c i t e d o r a
22
p r o to n a te d s i n g l e t s t a t e s p e c i e s ,
40E la d and R o s e n th a l i n v e s t i g a t e d p h o to d e c a r b o x y la t io n
r e a c t i o n s o f p u r i n e s . They fo u n d t h a t a l i p h a t i c a -am in o
a c id s w ere d e c a rb o x y la te d i n th e p re s e n c e o f c a f f e i n e , XV,
g iv in g 8- a l k y l c a f f e i n e d e r i v a t i v e s !
e . g .
CH,Nv^H
CH3
CH+ CH,CHCO,H
NH,
XV
No m echanism was p o s t u l a t e d ,
41S a n tu s e t a l a l s o r e p o r t e d t h a t i n th e p r e s e n c e o f
p u r in e s , am ino a c id s p h o to -d eco m p o sed to g iv e r a d i c a l s . They
p o s t u l a t e d t h a t e n e rg y t r a n s f e r o c c u r re d from th e p u r in e to
th e am ino a c i d .
R e a c t io n s In v o lv in g B ia c e ty l
42.Baum an d Norman d is c o v e r e d t h a t when a q u eo u s s o l u t i o n s
o f p h e n y la c e t i c a c i d , s u b s t i t u t e d p h e n y la c e t ic a c i d s , o r
p h e n o x y a c e t ic a c id w ere i r r a d i a t e d i n th e p r e s e n c e o f b i a c e t y l ,
d e c a rb o x y la t io n o f th e a c id o c c u r r e d . The o r i g i n o f th e
r e a c t i o n was b a s e d on a p o s s ib l e a n a lo g y w ith d e c a r b o x y la t io n43
o f th e s e a c id s e f f e c t e d by h y d ro x y l r a d i c a l s • th e s e a r e
e l e c t r o p h i l i c i n c h a r a c t e r and i n t h i s r e s p e c t re se m b le th e% / 44 45 \n , IT s t a t e o f c a rb o n y l compounds ( s e e f o r exam ple ' ) .
23
They fo u n d t h a t th e h i a c e t y l r e a c t i o n s w ere a c i d - c a t a l y s e d
and p o s t u l a t e d t h a t th e b i a c e t y l , i n i t s e x c i t e d n,Tr^ t r i p l e t
s t a t e , r e a c t e d by i n i t i a l e l e c t r o p h i l i c a t t a c k a t th e 'p a r a '
p o s i t i o n o f th e a r y l sy s tem I
e . g .
[MeCO.COMe] PhCHg GOgH
C H
CH3C —
- H
XVI
-CO2
M«CO.COM%So
CH,
HO. XHoc —c
The i n t e r m e d i a t e , XVI, so fo rm ed c o u ld e i t h e r g iv e g ro u n d
s t a t e r e a c t a n t s v ia p a thw ay [ i ] , o r f ra g m e n t v i a pa thw ay [ i i ]
g iv in g d e c a r b o x y la t io n . They s u g g e s te d t h a t th e r e a c t i o n
w ith p h e n o x y a c e t ic a c id p ro c e e d e d v i a an a n a lo g o u s m echanism .
The r a t e o f r e a c t i o n was f a s t e r w ith m -m e th o x y p h e n y la c e tic
a c i d th a n th e u n s u b s t i t u t e d a c id ,b e c a u s e th e m ethoxy s u b s t i
t u e n t a c t i v a t e d th e p a r a p o s i t i o n t o e l e c t r o p h i l i c a t t a c k
( c . f . th e g r e a t e r r e a c t i v i t y o f a n i s o l e com pared to b en zen e
24
• 46to w a rd s OH ) . . The p r o d u c ts i s o l a t e d from th e r e a c t i o n s
o f p h e n o x y a c e t ic a c i d and p h e n y la c e t i c a c i d w ith b i a c e t y l
w ere c o n s i s t e n t w ith th e m echanism p ro p o s e d i n t h a t th e y
i n d i c a t e d th e i n t e rm ed iacy o f th e phenoxyme t h y l and b e n z y l
r a d i c a l s , r e s p e c t i v e l y !
e . g .
Me/CO.COMe + PhCHg COgH -> PhCHg*
2PhCHg ' (PhCHa )g
MePhCHg + MeCO
COMe
—MeCO
PhCHg ——CO. Me
(B ib e n z y l an d b e n z y l m eth y l k e to n e a r e p r o d u c ts i s o l a b l e
from r e a c t i o n o f b i a c e t y l w ith p h e n y la c e t i c a c i d ) .
O th e r D e c a rb o x y la t io n R e a c tio n s
47Jo s h u a an d L ew is fo u n d t h a t on i r r a d i a t i n g b e n ze n e
s o l u t i o n s o f a z o b e n z e n e -2- c a r b o x y l i c a c i d s , d e c a r b o x y la t io n
to th e c o r r e s p o n d in g a z o b e n z e n e s o c c u r r e d . No r e a c t i o n was
o b s e rv e d w ith a z o b e n z e n e -3 - o r a zo b e n ze n e - 4 - c a r b o x y l ic a c i d s
and th e y s u g g e s te d t h a t th e Z w i t t e r io n fo rm , X V II, c o u ld
p la y a n e s s e n t i a l r o l e i n th e d e c a rb o x y la t io n !
25
b,c
N
XVII
( r s H.CHj .CI,
or NlCHjlj)
Maki and S u zu k i fo u n d t h a t i r r a d i a t i o n o f b e n ze n e
s o l u t io n s o f a l i p h a t i c c a r b o x y l ic a c i d s , c o n ta in in g 2-am ino-
th io p h e n o l , l e d to d e c a r b o x y la t io n . The p r o d u c ts i s o l a t e d
w ere 2 - m e t h y l t h i o a n i l i n e , X V III, and s e v e r a l 2 , 2 - d i a l k y l -
b e n z o th ia z o l in e s , XIX, h a v in g a lk y l g ro u p s a r i s i n g from
f r a g m e n ta t io n o f th e a lk y l r e s id u e o f th e a c id I
NH.
SH
+ RCOjH KbNH,
SÇH,+
XVIII XIX
They s u g g e s te d t h a t a p o s s ib l e m echanism in v o lv e d f r a g m e n ta t io n
o f th e a c id g iv in g v a r io u s a lk y l r a d i c a l s w hich a t t a c k e d th e
am in e .
49F u j i t a e t a l fo u n d t h a t a c e t i c a c id was p h o to d e c a r b
ox y l a t e d i n th e p re s e n c e o f c y c l i c o l e f i n s !
e . g .
kbCHgCOgH
+
OCCH,
26
They w ere u n c e r t a i n a s t o w h e th e r a r a d i c a l o r i o n i c
m echanism was o p e r a t i v e .
Summary
The p h o to d e c a r b o x y la t io n r e a c t i o n s re v ie w e d can be
d iv id e d i n t o th e f o l lo w in g c a te g o r ie s *
1 . D e c a r b o x y la t io n s v ia R a d ic a l s !
<s>e . g . PhCHsCOa ^PhC H g0%
- ÊPhCHg + COg
2 , D e c a rb o x y la t io n s v i a I o n s !
e . g .
CHpo^ — ^ — > <s> ,CH, + CO5
3 . D e c a r b o x y la t io n s In v o lv in g Ox.ygen T r a n s f e r !
e . g .J ^ 2 3
NO.
NOg
n r ’.crV o h
— COfl
NO
NOg
4 . D e c a rb o x y la t io n s v i a S a l t s !
e . g . Ce^O gCE + E* + COg
27
5 . D e c a rb o x y la t io n v i a I n i t i a l P ro to n T r a n s f e r !
e . g .
'O.CR
-C 0 <
p r o d u c ts
[ a= RCOgH]
6 . D e c a rb o x y la t io n s I n v o lv in g E l e c t r o p h i l i c a t t a c k !
e . g . ,
MeCO.COMe + PhCHg COg HCH
C —H.C
-CO.
p r o d u c ts
28
1 .3 A R eview o f P h o to d e c a rb o x y la t io n R e a c t io n s I n v o lv in g
B io c h e m ic a l S ystem s
I n t r o d u c t io n
A c l a s s o f compounds w hich h a s r e c e iv e d c o n s id e r a b le
a t t e n t i o n by b io c h e m is ts i n r e c e n t y e a r s a r e th e * ' f l a v i n s '*
The f l a v i n s t r u c t u r e i s b a s e d on a 7 , 8- d im e th y l i s o a l lo x a z in e
u n i t , w hich i s num bered a s i n d i c a t e d , (w here R i s an a l k y l
o r h y d r o x y la te d a l k y l g ro u p ) :
Much o f th e r e s e a r c h h a s in v o lv e d th e f o l lo w in g f l a v i n s :
L u m if la v in : R = Me
R ib o f la v in : R = -CHg - (CHOH )Q -CBg OH
F la v in M o n o n u c leo tid e (PMN): R = -CHg - (CHOH )a -CHg O-PO3H
F la v in A den ine D in u c le o t id e (FAD):
0 0
I «R = -C H 2 -(C H 0 H )a -C I^ -0 -P -0 -P -0 -C H 2
OH OH
OH OH
29
[ F la v in m o n o n u c le o tid e an d f l a v i n a d e n in e d i n u c l e o t id e w i l l
be r e f e r r e d to a s FMIT and FAD, r e s p e c t i v e l y ] ,
FMN an d FAD a r e known a s * ' f l a v i n c o e n z y m e s ''. The f l a v i n
u n i t i s fo u n d n a t u r a l l y i n some p r o t e i n s ; th e s e compounds
a r e known a s f l a v o p r o t e i n s , e . g . D -am ino a c i d o x id a s e , and
i t i s th e s t r u c t u r a l a n a lo g ie s b e tw een th e s e compounds an d
th e s im p le r f l a v i n s t h a t h a s p ro m o ted r e s e a r c h i n t o th e
r e a c t i o n s o f th e l a t t e r com pounds.
The f l a v i n u n i t i s p h o to re d u c e d i n many r e a c t i o n s ; i n
some c a s e s i t c an be r e g e n e r a te d w ith oxygen . The
f o l lo w in g re v ie w c i t e s r e a c t i o n s i n w hich th e f l a v i n u n i t
i s p h o to re d u c e d i n th e p re s e n c e o f a n a c i d , w hich i s
s im u lta n e o u s ly d e c a rb o x y la te d .
R e a c t io n s I n v o lv in g I n d o l e a c e t i c A c id
50G a ls to n was th e f i r s t t o d i s c o v e r t h a t i n d o l e a c e t i c
a c id was p h o to d e c a rb o x y la te d i n th e p r e s e n c e o f r i b o f l a v i n .
D u rin g a s e r i e s o f e x p e r im e n ts on th e p h y s io lo g y o f l i g h t
a c t i o n on p e a s , he n o t i c e d t h a t th e a d d i t i o n o f s m a ll
am ounts o f r i b o f l a v i n i n h i b i t e d g ro w th on e x p o su re to
l i g h t . He a l s o fo u n d t h a t a d d i t i o n o f l a r g e q u a n t i t i e s
o f i n d o l e a c e t i c a c i d , w hich i s known to be a g ro w th f a c t o r
i n p l a n t s , p a r t i a l l y r e v e r s e d t h i s i n h i b i t i o n ; i t t h e r e f o r e
a p p e a re d p o s s i b l e t h a t r i b o f l a v i n w as, i n some way,
p h o t o - i n a c t i v a t i n g th e i n d o l e a c e t i c a c i d . He fo u n d t h a t
on a e r o b i c a l l y i r r a d i a t i n g an aqu eo u s s o l u t i o n o f i n d o le -
30
a c e t i c a c i d c o n ta in in g r i b o f l a v i n ̂ (pH = 7 ) ; one m ole o f
oxygen was a b s o rb e d and one mole c a rb o n d io x id e l i b e r a t e d
p e r mole o f i n d o l e a c e t i c a c i d o x id i s e d . He c o n s id e r e d th e
fo l lo w in g r e a c t i o n scheme I
hORb
lAA + Eb*
RbHs + V a Ob
Eb
o x id a t io n p r o d u c t + RbH^
Rb + Hj 0
w here Rb i s a g ro u n d s t a t e r i b o f l a v i n m o le cu le ,
Rb* i s m o le c u le o f r i b o f l a v i n i n a n e x c i t e d s ta te ^
RbHg i s th e re d u c e d d ih y d r o r ib o f 1 a v i n ,
lAA i s i n d o l e a c e t i c a c i d .
RbHg: R = h y d r o x y la te d
s id e c h a in
[The above sym bols w i l l be u s e d i n a l l e q u a t io n s in v o lv in g
th e s e e n t i t i e s ] .
H ence, i n th e p re s e n c e o f oxygen th e r i b o f l a v i n i s
r e g e n e r a te d and h a s a n o v e r a l l c a t a l y t i c e f f e c t . The
fo l lo w in g e q u a t io n r e p r e s e n t s th e r e a c t i o n !
lAA + OgRb
hio x id a t io n p ro d u c t + CQg
31
N athanson^^ e t a l s t u d i e d th e n a tu r e o f th e o x id a t io nc 51
produc^dr; They n o te d t h a t M eyer h a d i d e n t i f i e d
in d o le a ld e h y d e a s th e f i r s t o x id a t io n p ro d u c t o f th e r e a c t io n , 51
N ath an so n e t a l c o n firm e d t h i s p r o d u c t and p ro p o s e d th e
f o l lo w in g r e a c t i o n schem e!
pH = 3 .6 to 7 .5
lAA +HgO/CCC^H
oI I
^CCOgH CHO
+0 %
2Rbhü
2Rb
2Rb* + 2H ® + 2 e ^ 2RbH*
2RbH* + 2H ^ + a e 2RbHg
T h e re fo re o v e r a l l !
lA A + 2Rb + HgO 2RbHg +
+ COg
CHO
32
I n th e p re s e n c e o f oxygen th e d i h y d r o r ib o f l a v i n i s
o x id is e d b a ck t o r i b o f l a v i n .
RbH' :
H.C
NH
R = h y d r o x y la te d
s id e c h a in
They p ro p o s e d t h a t r e a c t i o n p ro c e e d e d v ia a t r i p l e t s t a t e o f
r i b o f l a v i n a s q u e n ch in g by p o ta s s iu m io d id e , a known53t r i p l e t q u e n c h e r , was o b s e rv e d . The s i n g l e t s t a t e was
d is c o u n te d a s r i b o f l a v i n f lu o r e s c e n c e was n o t quenched by
i n d o l e a c e t i c a c i d . In v o lv e m e n t o f com plex f o rm a t io n was
a l s o d i s c o u n te d a s th e quantum y i e l d f o r d e s t r u c t i o n o f
i n d o l e a c e t i c a c i d i n c r e a s e d w ith i n c r e a s in g te m p e r a tu r e .
The maximum quantum y i e l d f o r i n a c t i v a t i o n o f i n d o l e a c e t i c
a c i d was fo u n d t o be 0 . 7 1 , i n d i c a t i n g a h ig h ly e f f i c i e n t
r e a c t i o n . Prom th e s e r e s u l t s th e y d ed u ced t h a t r e a c t i o n
o c c u r re d on e v e ry e n c o u n te r o f a n i n d o l e a c e t i c a c i d
m o le cu le w ith a m o le c u le o f r i b o f l a v i n i n i t s t r i p l e t s t a t e
i . e . r e a c t i o n i s d i f f u s i o n c o n t r o l l e d .
]
R e a c t io n s I n v o lv in g Amino A c id s
The a e r o b ic p h o to d e c a r b o x y la t io n o f am ino a c i d s ,
c a t a ly s e d by r i b o f l a v i n a n d PMN, was f i r s t r e p o r t e d by 54
P r i s e l l e t a l . They fo u n d t h a t fo rm ald eh y d e was a m a jo r
p r o d u c t a s w e l l a s c a rb o n d io x id e a n d , u s in g c a r b o n - 1Z4.
i s o t o p i c l a b e l l i n g s t u d i e s , ded u ced t h a t th e fo rm ald eh y d e
33
was d e r iv e d a lm o s t e x c l u s i v e l y from th e a -c a rb o n o f th e
am ino a c i d , e . g . f o r s a r c o s in e !
pH = 7*8
£ SixRb + H3 C-NH-CH2-CO2 H + H3O
* XXRbHg + H3 CNIij + CHg 0 + COg
RbHg + Og -+ Rb + HgOg
X XXw here C a n d G a r e [^* 0 ] i s o t o p i c a l l y l a b e l l e d c a rb o n s . The
d ih y d r o f la v in was o x id is e d b a ck to th e f l a v i n u n d e r th e
a e r o b ic c o n d i t i o n s . R e a c tio n s o f am ino a c i d s , and some
am in es , w ere fo l lo w e d by oxygen u p ta k e ( m a n o m e tr ic a l ly )
and fo rm ald eh y d e fo r m a t io n ( s p e c t r o p h o t o m e t r i c a l l y ) and th e
r e s u l t s a re shown i n th e t a b l e t
G ly c in e 2 1 .6
(N-Me t h y l ) g ly c in e 10 9 .9
(N-Diin e th y l ) g ly c in e 12 1 2 .8
B e ta in e -c 1 0
E th y l e n e d i a m i n e t e t r a - a c e t i c i h 1 2 .4a c id
M ethylam ine ^ 1 0 .1
D im ethy lam ine 4 2 .5
Trim e th y la m in e 9 8 .3
A c e ta te 0 0
T r im e th y la c e ta te 0 0
V a le r a te 0 0
34
The v a lu e s g iv e n a r e f o r s o l u t io n s o f 20 ^ m o le s o f s u b s t r a t e
and 1 y m ole PMN d i s s o lv e d i n 2*4 m l. 0*075 M p o ta s s iu m
p h o sp h a te b u f f e r , pH = 7 .8 , an d i r r a d i a t e d f o r f i v e h o u r s .
They w ere u n a b le t o d e t e c t th e i n te r m e d ia te fo rm a t io n
o f a k s to a c i d , su c h a s g ly o x y l ic a c i d from th e s a r c o s in e
e x p e r im e n ts . M o reo v er, a d d i t i o n o f g ly o x y l ic a c i d to th e
r e a c t i o n m ix tu re d id n o t l e a d t o an i n c r e a s e i n fo rm a ld eh y d e
fo rm a t io n , u n d e r th e same c o n d i t i o n s . I n c lu d e d i n th e
t a b l e a r e r e s u l t s o b ta in e d w ith some a m in e s . The f a c t t h a t
r e a c t i o n o c c u re d w ith th e s e compounds a n d n o t w ith th e
c a r b o x y l ic a c id s i n v e s t i g a t e d , e . g . a c e t a t e , v a l e r a t e ,
i n d ic a t e d t h a t th e p re s e n c e o f a n i t r o g e n atom i n th e
s u b s t r a t e was a p r e r e q u i s i t e f o r r e a c t i o n to o c c u r . By
i n c r e a s in g th e s u b s t i t u t i o n on th e n i t r o g e n a tom , i n b o th
th e g ly c in e and m eth y lam in e s e r i e s , th e oxygen u p ta k e and
fo rm ald eh y d e y i e l d s i n c r e a s e d . H ence, th e r e a c t i o n was
fa v o u re d by th e i n c r e a s e d a v a i l a b i l i t y o f th e n o n -b o n d in g
e l e c t r o n s on th e n i t r o g e n a to m . They p ro p o s e d two
m echanism s f o r th e r e a c t i o n s w ith am ino a c i d s , b o th i n v o lv in g
a n i n i t i a l h y d rid e* * t r a n s f e r t o th e f l a v i n , i . e . t r a n s f e r
o f a p r o to n a n d two e l e c t r o n s in one s t e p . T hese a re
shown i n p a th w ay s ( i ) a n d ( i i ) Z
35
H' \ « i » I • •
N C — C 0 0/ I
H
R
eN ' C ——C 0 0
H
R
R
OH
N — C — “H
H
( 1 1 )
E—' *■ C 0 0
RI
H
R3 NH + HCHO
P athw ay ( i ) In v o lv e s h y d ro g en a b s t r a c t i o n from th e a C-H
bond a n d e l e c t r o n t r a n s f e r from th e c a rb o x y l g ro u p ;
pathv /ay ( i i ) in v o lv e s h y d ro g en a b s tr a c t io n from th e a C-H bond
b u t e l e c t r o n t r a n s f e r from th e n i tro g e n * The a u th o r s
c o n s id e r e d t h a t th e l a t t e r pa thw ay was m ost l i k e l y i n v iew
o f th e a p p a r e n t in v o lv e m e n t o f th e n o n -b o n d in g e l e c t r o n s
on n i t r o g e n . The am in es c a n , o f c o u r s e , o n ly r e a c t by a
pa thw ay a n a lo g o u s to ( i i ) .
36
N ic k e rs o n an d S t r a u s s have shown t h a t th e a n a e ro b ic
p h o to ly s i s o f an aq u eo u s s o l u t i o n o f m e th io n in e c o n ta in in g
r i b o f l a v i n gave m e th io n in e s u lp h o x id e , by i t s d i f f e r e n t i a l
c h ro m a to g ra p h ic R f v a lu e ; th e y d id n o t r e p o r t d e c a rb o x y la
t i o n o f th e a c i d . E nns an d B u rg e ss n o te d t h a t Patton^^
h ad r e p o r t e d th e p r o d u c t io n o f 3 - ( n ie th y l th io ) p r o p io n a ld e h y d e
from aq u eo u s m e th io n in e - r i b o f l a v i n s o l u t i o n s e x p o sed t o
s u n l i g h t i n th e p re s e n c e o f a i r . E nns e t a l c o n firm e d
th e fo rm a t io n o f t h i s p r o d u c t p o l a r o g r a p h ic a l l y an d a l s o
q u a l i t a t i v e l y d e m o n s tra te d th e p re s e n c e o f am m onia. The
o v e r a l l r e a c t i o n i s ;
hdR b + CHa SCHg CHg CHCOg H + Hg 0 — Rb Hg + NH3 + COg +
NHg CH aSCH gCH gCH O
58Byrom an d T u rnbuH e x te n d e d th e r e a c t i o n by s tu d y in g th e
a n a e ro b ic o x id a t io n o f a -am in o a c id s e . g . , m e th io n in e ,
s e r i n e , p h e n y la la n in e , by f l a v i n s and f l a v i n coenzym es e . g . ,
r i b o f l a v i n , l u m i f l a v i n , PMN,and PAD. They fo u n d t h a t
ammonia was fo rm ed a s w e l l a s a k e to a c i d , w hich i n some
c a s e s d e c a rb o x y la te d , d e p e n d in g on i t s s t a b i l i t y , t o g iv e
th e c o r re s p o n d in g a ld e h y d e . They p o s t u l a t e d th e f o l lo w in g
r e a c t i o n schem e!
pH=7
RCH — GOgH + P _ R O — COgH + ( l )\ II
HH
E C — COigH + % 0 ---------- >- E C — COgH + NHgII HHH 0
E C — COgH > - ECHO + COg
0
37
w here F i s g ro u n d s t a t e f l a v i n ,
Fq i s s i n g l e t s t a t e f l a v i n , o± /
F^^ i s t r i p l e t s t a t e f la v in ^
FHg :
The t r i p l e t s t a t e h a s b e e n shown to be th e e x c i t e d s t a t e59
r e s p o n s ib le f o r th e p h o to c h e m is try o f f l a v i n s and th e y
su g g e s te d t h a t th e t r i p l e t s t a t e o f th e f l a v i n was r e s p o n s ib l e
f o r d e h y d ro g e n a tio n o f th e am ino a c id i n s t e p ( l ) . They
p ro p o se d t h a t r e a c t i o n o c c u r re d from a com plex a n d t h a t th e/
h ig h e f f i c i e n c y o f r e a c t i o n s o b se rv e d w ith some am ino a c id s
e . g . , m e th io n in e , was due to th e h e te r o atom i n th e s id e
c h a in h a v in g a s t a b i l i s i n g e f f e c t on th e com plex .
60I n a n o th e r p a p e r , Byrom and T u rn b u ll s t u d i e d th e
k i n e t i c s o f th e s e r e a c t i o n s . They lo o k e d i n d e t a i l a t t h e
lu m if la v in - m e th io n in e sy s tem an d t h e i r r e s u l t s s u g g e s te d
t h a t th e r e a c t i o n was d i f f u s i o n c o n t r o l l e d , th e i n i t i a l
p r o c e s s b e in g a one e l e c t r o n t r a n s f e r from m e th io n in e t o a
v a c a n t o r b i t a l i n th e e x c i t e d f l a v i n .
P e n z e r and Radda®^ s tu d ie d i n d e t a i l th e p h o to d e c a rb
o x y la t io n o f a -p h e n y lg ly c in e i n th e p re s e n c e o f f l a v i n s .
38
The p r o d u c ts th e y o b ta in e d a re r e p r e s e n te d i n th e f o l lo w in g
e q u a t io n !
pH> 6h )
PhCHCQaH + P + % 0 ---------* - PhCHO + CO3 + NH3 + F%
NHa
They d id n o t d e t e c t p h e n y lg ly o x y l ic a c i d i n th e r e a c t i o n
m ix tu re and th e y a l s o s u g g e s te d t h a t a n i n i t i a l one e l e c t r o n
t r a n s f e r from am ino a c id to e x c i t e d f l a v i n was l i k e l y .
R e a c t io n s I n v o lv in g P h e n y la c e ta te I o n s
The r e a c t i o n s so f a r c o n s id e r e d have b e e n c o m p le te ly
r e v e r s i b l e i . e . th e f l a v i n can be r e g e n e r a te d by r e a c t i o n
w ith oxygen , and no s t a b l e a d d u c ts b e tw een th e d e c a rb o x y la te d61
a c id and re d u c e d f l a v i n r e p o r t e d , Hemmerich e t a l
(an d W alk er e t a l ^ ) r e p o r t e d a p h o to d e c a rb o x y la t io n
r e a c t i o n i n w hich th e f l a v i n was i r r e v e r s i b l y p h o to re d u c e d .
When an aqu eo u s s o l u t i o n o f 3 - m e th y l lu m if la v in c o n ta in in g
p h e n y la c e ta te io n s was i r r a d i a t e d , u n d e r a n a e ro b ic c o n d i t i o n s ,
a q u a n t i ty o f c a rb o n d io x id e was e v o lv e d s t o i c h i o m e t r i c w ith
th e am ount o f f l a v i n r e d u c e d . Two ad d u c ts ,X X and X X I,w ere
i s o l a t e d from th e r e a c t i o n m ix tu r e . XX r e a c t e d r e l a t i v e l y
s lo w ly w ith oxygen to g iv e XXE w hich was s t a b l e to oxygen
ev en i n th e p re s e n c e o f l i g h t . XXI was s t a b l e t o oxygen i n
th e a b sen c e o f l i g h t b u t was o x id i s e d , i n th e p re s e n c e o f
l i g h t , b ack t o 3 - m e th y l lu m if la v in , They s u g g e s te d t h a t th e
N5 p o s i t i o n on th e f l a v i n was o f im p o rta n c e i n c h e m ic a l
r e a c t i v i t y and p ro p o s e d two p o s s ib l e m echanism s in v o lv in g
39
e i t h e r g roup t r a n s f e r o r i n i t i a l e l e c t r o n t r a n s f e r ,
XX
HC
NCKKC
O
PkCHgCOg<s>
CH, H
Y + " 3C
(s lo w )
XXICH,
Pk O
NCH3
G roup T r a n s f e r i . e . c o n c e r te d l o s s o f c a rb o n d io x id e I
NCH3
PhCHgY0=0
<s>HC,
NCtyHC
PhCH. + H'
XX
(A dduct XXI w ould be fo rm ed i n an a n a lo g o u s m an n e r) .
40
I n i t i a l E le c t r o n T r a n s f e r
+ (t>ci^cq.e le c t r o n
t r a n s f e r_|_ (|)CHgC02 '
H -c%
FH*
PH*î\
A dduct
V
/
R e a c tio n s I n v o lv in g P y ru v ic A c id
64De Kok a n d V e eg e r r e p o r t e d t h a t by i r r a d i a t i n g a
f l a v o p r o t e i n i . e . D -am ino a c id o x id a s e , i n th e p re s e n c e o f
i s o t o p i c a l l y l a b e l l e d c a rb o n -1 4 p y r u v ic a c i d , th e t h i n l a y e r
chrom atogram o f th e r e a c t i o n m ix tu re i n d i c a t e d t h a t r a d i o
a c t i v i t y was a s s o c i a t e d w ith th e f l a v i n , s u p p o r t in g th e id e a
o f an a d d i t i o n compound. They c o u ld n o t f i n d any e v id e n c e
f o r a d d u c t f o r m a t io n on r e p l a c in g th e f l a v o p r o t e i n w ith th e
coenzyme FAD, B r u s t l e i n and Hemmerich , h o w ev er, d e te c t e d
a n a d d i t i o n compound on i r r a d i a t i o n o f a n aq u eo u s s o l u t i o n
o f 3 - m e th y l lu m if la v in c o n ta in in g p y ru v ic a c i d o r i t s s a l t s .
I n th e a b se n c e o f oxygen a r e v e r s i b l e p h o to r e d u c t io n , ( a ) ,
was th e p re d o m in a n t r e a c t i o n . On c o n tin u o u s a d m is s io n o f
oxygen^ ho w ev er, t h i s r e a c t i o n was s u p p r e s s e d and a s lo w e r
i r r e v e r s i b l e p h o to r e d u c t io n , w ith d e c a r b o x y la t io n o f th e
a c id , ( b ) , became m arked and f i n a l l y q u a n t i t a t i v e :
41
CH3 COCO2 H +
(o r CHgCOCOa^)
IN
H.0
NH
O
O
( b )
COCH.X X III
The a d d u c t X X III was i s o l a t e d from th e r e a c t i o n m ix tu r e ,
p h o to ly s e d u n d e r a e r o b ic c o n d i t i o n s . They s u g g e s te d t h a t
t h e r e w ere two p o s s ib l e m echanism s f o r th e r e a c t i o n . The
f i r s t in v o lv e d a * ‘h y d rid e* * t r a n s f e r from th e a c id t o th e
f l a v i n ; th e se c o n d m echanism in v o lv e d a g roup t r a n s f e r w ith
c o n c e r te d l o s s o f c a rb o n d io x id e . They did n o t e n la r g e on
th e f e a s i b i l i t y o f th e two m echanism s.
 P o s s ib le G e n e ra l M echanism
66W eatherby and C a r r h ave t r i e d to com bine a l l th e
known f l a v i n - s e n s i t i s e d p h o to d e c a rb o x y la t io n r e a c t i o n s , o f
c a r b o x y l ic a c i d s , u n d e r one common m echanism . They
i n v e s t i g a t e d th e p h o to o x id a t iv e d e c a rb o x y la t io n o f d ih y d ro -
p h t h a l a t e s c a t a l y s e d by r i b o f l a v i n and 3 - m e th y l lu m if la v in .
B e n zo ic a c id was fo u n d t o be a p ro d u c t o f th e r e a c t i o n .
42
FH
A h y d r id e t r a n s f e r m echanism was d is c o u n te d i n f a v o u r o f a
r a d i c a l m echanism in v o lv in g a one e l e c t r o n t r a n s f e r from th e
a n io n to th e f l a v i n , w i th in a com plex , a s th e i n i t i a l s t e p .
They p ro p o s e d th e f o l lo w in g r e a c t i o n schem eI
pH 4 t o 8
com plexf o rm a t io n
F
CO,H
e l e c t r o nt r a n s f e r
1 r- -
CO /
COg CO^H
+ H
-F H
h y d ro g e na b s t r a c t i o n
rco^H+ FH,
CO„H
The f l a v i n was r e g e n e r a t e d i n th e p re s e n c e o f oxygen I
PHg + Og P + H2 Q3
The e f f e c t o f pH on th e r e a c t i o n s s u g g e s te d t h a t th e i o n i s e d
f r e e c a rb o x y l g ro u p was an im p o r ta n t f a c t o r t o th e r e a c t i o n
s in c e th e d e c a r b o x y la t io n r e a c t i o n c lo s e l y p a r a l l e d th e
i o n i s a t i o n o f th e c a rb o x y l g ro u p .
They r a t i o n a l i s e d th e r e a c t i o n b e tw een f l a v i r s a n d
p h e n y la c e t a t e io n s by a s i m i l a r m echanism I
43
(g* com plex+
fo rm a t io n
PH*
<)CHs-COc F H '
(jlCHaCOa *
a d d u c ts
e l e c t r o nt r a n s f e r
The b e n z y l r a d i c a l was n o t l i a b l e t o f u r t h e r h y d ro g e n
a b s t r a c t i o n an d r a d i c a l p a i r i n g o c c u r r e d t o g iv e th e o b s e rv e d
a d d u c ts ,
They a l s o c o n s id e r e d th e p h o to d e c a r b o x y la t io n o f am ino 54 , 55 ,58
F a c to r s v/hich54
a c id s by f l a v i n s ' by t h i s m echanism .54i n c r e a s e d th e e l e c t r o n d e n s i ty on th e am ino g ro u p w ould
a l s o in c r e a s e th e e l e c t r o n d e n s i ty on th e i o n i s e d c a rb o x y l
g roup an d h en ce e l e c t r o n t r a n s f e r from th e l a t t e r t o th e
f l a v i n w ould be f a c i l i t a t e d !
EN - C H g C o P
e l e c t r o nt r a n s f e r
com plex
PHh y d ro g e n
a b s t r a c t i o n
( h y d r o ly s i s )
4 4
(H ow ever, t h i s m echanism r e q u i r e s a n N-H bond to be p r e s e n t i n
th e am ino a c id and c a n n o t a c c o u n t f o r th e d e c a rb o x y la t io n o f
t e r t i a r y am ino a c i d s e . g . (N -d im e th y l) g ly c in e . I t a l s o
d o es n o t a c c o u n t f o r th e fo r m a t io n , in some in s ta n c e s ,^ * o f
th e cc-keto a c i d ) .
61P e n z e r an d R adda p ro p o se d t h a t th e d e c a r b o x y la t io n s
6a. 54in v o lv in g p h e n y la c e t a t e and am ino a c id s p ro c e e d e d by
d i f f e r e n t m echan ism s. T h is was b a s e d on th e o b s e r v a t io n
t h a t th e r e a c t i o n in v o lv in g p h e n y la c e ta te was i r r e v e r s i b l e ,
w hereas th o s e in v o lv in g am ino a c id s w ere r e v e r s i b l e by
oxygen ; a l s o a - p h e n y lg ly c in e showed a pH dependence w hich
in d ic a t e d t h a t r e a c t i o n o n ly p ro c e e d e d a t pH 6 i . e . when
^CHg(HHg )C o j^ was p r e s e n t , w h ereas d e c a rb o x y la t io n s w ith
p h e n y la c e ta te w ere r e l a t i v e l y p H - in d e p e n d e n t.
D e c a rb o x y la t io n s I n v o lv in g M ethy lene B lue
The r e a c t i o n s o f m eth y len e b lu e have b e e n in c lu d e d i n
t h i s s e c t i o n b e c a u se o f a p o s s i b l e a n a lo g y b e tw een th e
m echanism o f th e s e r e a c t i o n s and r e a c t i o n s in v o lv in g f l a v i n s .
67G oodspeed e t a l have i n v e s t i g a t e d th e p h o to -o x id a tio n
o f t e r t ia r y n i t r o g e n compounds by m eth y len e b lu e . The
p r o d u c ts th e y o b ta in e d from p h o t o ly s i s o f an aq u eo u s
s o l u t i o n o f ( N - d i e t h y l )g ly c in e c o n ta in in g m e th y len e b lu e
w ere a s f o l lo w s !
45
pH - 7
MB + EtaNCHaCOs® + HgO
MBH + C p a + E t^ N H + CHgO
Vk\>
MBS>MBH
N(CHj)j N(CHj)2
A one e l e c t r o n t r a n s f e r from th e a c i d a n io n t o th e dye was
d is c o u n te d a s th e r a d i c a l s p ro d u c e d w ould n o t have b e en
e x p e c te d to g iv e th e o b se rv e d p r o d u c ts !
MB ® + EtaNCHaCOa^e l e c t r o n
t r a n s f e r■*- [MB' ] + EtgNCHa '+ CO;
They s u g g e s te d t h a t th e r e a c t i o n in v o lv e d an i n i t i a l e l e c t r o n
t r a n s f e r from h y d ro x id e io n to th e d y e , fo l lo w e d by h y d ro g en
a b s t r a c t i o n from th e a c i d a n io n , and su b s e q u e n t o x id a t io n o f
th e am ine r a d i c a l by OH* :
[MB ® ] + OH'"' -* [MB' ] + OH'X . a
&[M B'] + EtaNC^COg -» MBH + EtaNCHCOa
EtaNCHCO^ E t g N c f COg ' -* EtgNOT + C%
E t a l ^ + E ta
Et^jNCHa' + OH' EtgNH + C% 0
46
The h y d ro g en a b s t r a c t i o n s te p w ould be fa v o u re d by s u b s t i t u
e n t s on th e n i t r o g e n an d th e m echanism p ro v id e d f o r a l l th e
o b se rv e d p r o d u c t s .
Summary
The p h o to d e c a r b o x y la t io n r e a c t i o n s o f am ino a c i d s ,
p y ru v ic a c i d , p h e n y la c e ta t e i o n s , and d ih y d r o p h th a la t e s , i n
th e p re s e n c e o f f l a v i n s , have b e en re v ie w e d . The r e a c t i o n
o f m eth y len e b lu e w ith am ino a c id s i s in c lu d e d i n t h i s
s e c t i o n .
47
CHAPTER 2
PHOTOINDUCED DECARBOXYLATION OF
CARBOXYLIC ACIDS SENSITISED BY
CARBONYL COMPOUNDS.
48
2 .1 R e s u l t s and D is c u s s io n
2 .1 .1 P re l im in a r y P h o to d e c a r b o x y la t io n S t u d i e s .
I t was fo u n d t h a t when b en zen e s o l u t i o n s o f c a r b o x y l ic
a c i d s , o f th e ty p e RXCHjCOgH, (w here *R' i s a n a lk y l o r
a r y l g ro u p , an d *X* = 0 , 8 , o r N H ) , c o n ta in in g c e r t a i n
c a rb o n y l com pounds, w ere i r r a d i a t e d , d e c a rb o x y la t io n o f th e 68
a c id o c c u r re d , The c a rb o n d io x id e e v o lv e d i n th e
r e a c t i o n s was p r e c i p i t a t e d a s b a riu m c a r b o n a te , by p a s s a g e
th ro u g h a s a t u r a t e d b a riu m h y d ro x id e s o l u t i o n . The w e ig h t
o f c a rb o n a te o b ta in e d gave a q u a n t i t a t i v e m easu re o f th e
c a rb o n d io x id e p ro d u c e d . The y i e l d s o f c a rb o n d io x id e from
th e d e c a rb o x y la t io n o f s e v e r a l c a r b o x y l ic a c id s ( i . e . (pheny l-
t h i o ) a c e t i c a c i d , p h e n o x y a c e t ic a c id , S - ( n - b u t y l t h i o ) a c e t i c
a c id , and N - (o -c h lo ro p h e n y l )g ly c in e ,) a r e shown i n T a b le 1 .
9 , 10-A n th ra q u in o n e , 9 , 10 -p h e n a n th ra q u in o n e , t e t r a c h l o r o - p -
b e n z o q u in o n e , p -b e n z o q u in o n e , b en zo p h en o n e , an d b i a c e t y l
were th e c a rb o n y l compounds u s e d a s s e n s i t i s e r s i n th e s e
p r e l im in a r y s t u d i e s . [ i t was l a t e r fo u n d t h a t x a n th o n e ,
2- a c e ty ln a p h th a le n e , f lu o r e n o n e , and a c e to p h e n o n e c o u ld
a l s o b r in g a b o u t th e d e c a rb o x y la t io n o f th e a c i d s ] .
I t can be s e e n t h a t b i a c e t y l c an b r in g a b o u t th e
d e c a rb o x y la t io n o f th e a c id s i n b en zen e s o l u t i o n , a s w e l l
a s aq u eo u s s o l u t i o n . I t was fo u n d t h a t p h e n y ls c e t i c
a c id was n o t de c a rb o x y l a t e d i n th e p re s e n c e o f benzophenone
o r th e q u in o n es ; i n c o n t r a s t , ho w ev er, a 17% y i e l d o f c a rb o n
49
ü •H•H xîrH •Ph rHK >5O ■P
dPh pq0 1ü d
u 1o co0do•H-P 1d orH • P4O 0 O0 0 rH
d Xî0 g üd d 10 •H ON diP! o 10rO fd
d0o0M 0 1
P! d ---NO o O•H -p •H-P 0 Xî0 M •P•H rH'd U b0 o dPi 0p4 0 xî•H ü
dS 0O 0Ph 0U d
P0 ü"d 0 •H•H xî •P« -P 0O ü•H d 0fd ♦H bPî 0 oo »d d
•H 0Ph ü XI0 0 P4ü
<fHO
0'drH0•H>H
0H,QEh
•HüCOü•H
8CO
n•Hü>5W)
0
"d•Hü0ü•H•P0ü0
•Hü0
Vû00
00
0000
1♦H
&2 gü
toH
CTk
pi
S
0\
m00
Vûr-
\oa \
s
00
C\J
rH xj- Œ\o\
BB
0 •Hd do cMd O•H Nd da* 00 Pd 1 0Xî d•P od o d
d •H§ o d0 (—IXî xî OPH1
ü N0 d
O d 0rH +> pq
#» 0 10^ Eh A
o00
00cr\
K\
00(T.
(M
CM
dO•(H•Pü0CQ
000
<1—1
0dd*d0üodA
do•H+30•H
VX)rH 0
ddH
*
I
Id0PQ
I—I
0Ü0•HPQ
50
d io x id e was r e c o rd e d f o r th e r e a c t i o n s e n s i t i s e d by b i a c e t y l .
W ith th e same i r r a d i a t i o n c o n d i t io n s a s w ere em ployed
f o r r e a c t i o n s r e p o r t e d i n T ab le 1 , benzophenone was fo u n d to
s e n s i t i s e th e d e c a rb o x y la t io n o f some s u b s t i t u t e d p h e n y la c e t ic
and p h e n o x y a c e t ic a c i d s . The r e s u l t s a re shown i n T a b le 2 .
T ab le 2 . Y ie ld s {%) o f c a rb o n d io x id e from i r r a d i a t i o n
o f b en zen e s o l u t i o n s o f some s u b s t i t u t e d a c i d s .
i n th e p re s e n c e o f b e n zo p h e n o n e .
A c id % Y ie ld C arbon D io x id e
4-Me th o x y p h e n y la c e t i c 49
3 -M e th o x y p h e n y la c e tic 18
( c . f . P h e n y la c e t i c ) 0
3 , 5 -D im e th o x y p h en o x y a ce tic 87
( c . f . Phenoxyac e t i c ) 34
I t c an be s e e n t h a t th e a d d i t i o n o f m e th o x y - s u b s t i tu e n ts
to th e a ro m a tic sy s tem o f p h e n o x y a c e t ic a c id g r e a t l y e n h an c es
th e e f f i c i e n c y o f th e d e c a r b o x y la t io n r e a c t i o n ; s i m i l a r l y ,
w ith p h e n y la c e t ic a c i d , w here th e i n c l u s i o n o f a methoxy-^
s u b s t i t u e n t r e n d e r s th e a c id r e a c t i v e . T hese r e s u l t s
i n d i c a t e t h a t th e p re s e n c e o f a h e te r o atom i n th e a c id
m o le c u le , e . g . th e oxygen atom o f th e m eth o x y -g ro u p i n
3-me th o x y p h e n y la c e t ic a c i d , may be a p r e r e q u i s i t e f o r th e
d e c a rb o x y la t io n r e a c t i o n t o p ro c e e d .
51
2 .1 .2 P ro d u c t s t u d i e s f o r R e a c t io n s I n v o lv in g A ro m a tic
K e to n e s .
The f o l lo w in g p ro d u c t s t u d i e s w ere c a r r i e d o u t i n o r d e r
to a i d e l u c i d a t i o n o f th e r e a c t i o n m echanism .
Y ie ld s o f S u b s t i t u t e d H y d ro carb o n s
One o f th e m a jo r p r o d u c ts o f th e d e c a r b o x y la t io n r e a c t i o n s
a r e s u b s t i t u t e d h y d ro c a rb o n s , o f ty p e RXCHq ; t h e f o l lo w in g
s t u d i e s w ere c a r r i e d o u t to a s c e r t a i n th e y i e l d s o f th e s e
p r o d u c t s .
I n o r d e r t o d e m o n s tra te th e in te rm e d ia c y o f r a d i c a l s o f
ty p e RXCHq *, a good h y d ro g e n d o n o r , t h io p h e n o l , was added t o
th e r e a c t i o n m ix tu r e s , w ith a v iew to i n c r e a s in g th e y i e l d s
o f s u b s t i t u t e d h y d ro c a rb o n s .
PhSH + RXCHg* RXCH3 H- PhS*
2PhS* -* (P hS )2
The y i e l d s o f s u b s t i t u t e d h y d ro c a rb o n s , from i r r a d i a t i o n
(p ro c e d u re B - s e e s e c t i o n 2 .2 ) o f benzene s o l u t i o n s o f
c a r b o x y l ic a c i d s , c o n ta in in g a ro m a tic k e to n e s , i n th e p re s e n c e
and a b se n c e o f th io p h e n o l , w ere d e te rm in e d by g a s - l i q u i d
c h ro m a to g ra p h y . The d e c a rb o x y la t io n o f p h e n o x y a c e t ic a c id ,
( p h e n y l t h i o ) a c e t i c a c i d , S- ( n - b u ty 1 t h i o ) a c e t i c a c i d , a n d
If _ ( o - c h i o r ophe ny 1 ) g ly c in e , s e n s i t i s e d by b e n zo p h en o n e ,
x a n th o n e , f lu o r e n o n e , 2- a c e ty ln a p h th a le n e , and a c e to p h e n o n e .
52
•H
•d•HÜ0
Ü•H■P0Ü0>?KOPJ0SiP
<Ho0do•H■P •d 0rH 0O PI0 O
-P0 0Pi Ai0N ÜPÎ •H0 +:XI 0
G<iH Oo Ph
PI 0o <H•H OP>0 0•H Ü»d Pi0 0P4 0Ph 0•H Pr
PBO 0Ph XI<iH -P
0rHo0•HPI044O
07drH0•H>H
aa
•H fH
0 'w •HId 0 0 S
H
'O .0 On 0 •p O H o O 0) 0
rH *HPh 0 PÎ O *H <£ Ü >)
2
0
0'd *HH d 0 <C -H ,
<po
•d
0̂ o
rH
§0 "d XÎ 0§•:§ •H <C
g
Jo o
0Ü
m
oCM
CMrH
s
iIPÎfS
oCM
lACM
ACM
CM CM rHcr\
lACM
I—ICM
(ArH
oo CArH
r^00CO CO
lAr -
ÎS
CM CO COrH
CM VO h- _d" CTkrA CM
COx t
CACM
II
lACM
lACM
CM CM
CMrH P
VO
oLA
B0iH04-P 0
B g dg S 52 : &O Ü P>d < 0k <
»d0-p0
gX)u0Ü0*d
»d
Ü0
U ido 00
■p dp
g <
B 00 p
d0 •d4 0■p ÜoP po And P0 O0 •H0 +>X» 0
♦Hid IdrH 00 P•H P>H M
H H -Kh-
d00«
a
&♦H
g
0 d1•H
g
* 4 —
53
«Po
0po•HP 0d 0rH PO O0 P
00 AiP0 üN •HP p0 0A B
O4h PO 0
P <HO O•HP 00 ü•d P"d 00 0P 0P P•H PS 0o Xîp P4h
P0 Pid•H idxî pp üA 0d0 ü
PrH P
0P ü0 0XîP O
PrH Xîh p
rHP b0 pB 0
Xî«H pO
0"drH0P>H
xt
0rHX>0Eh
g ip ^p0 0 lA lA LA LA LA LAP B •Td p 0 Eh P P H
rA rA p H vû VO vû VO I—1 1—1
•dH0
ê
0 -P 0 •P 0 ü B H
2 4h & P O 0 O Xî
ü A
'd•H
A
rH "P rH0 0 ^ •H S R
O A
fdy (ÿS “^ o
r0 »d
I Ir«d
H O
I I
0ü
LA O rA O
rH
OrA
lA00 3
*
§p
INP
A
3
o VOlA rA
cr\00
tü
iI%
rACTN
cr\ (AM CM
lA VO 00 (A
*
IOd
A
r-
CACM
00rA
00Vû
rArA
3
P0
gxî
IH
P?
8<I
CM
CMh-
OCM
00CM
rA00 0000
rHrA
r-r-
lArA
*
§
I§■p8<
nd•Hü0
%I0I§id000AidrH0S
•dsCO
rH&o■g0U
ê
p-P pP 00 00 0Xî P0 PP PO OP P0 0a XîP pO oP px; xî54 Eh
M 4 -
54
po0Popp •d 0p 0o P0 O
P0 0P Ai0N ÜP p0 pA gP oO p
0Po <Hp op0 0P o•d p0 0
0p 0p P
A6O 0P AU P
0 PId PpA IdP pP Üd 00
Op P
âP0
p Ü0 08
OP P>5 AP Pd PA >:I Pp d
Ap Io p0 1<d COP0PÎH
lA0
PA0EH
g f i
0 lA r -P 0 CM VO lA LA LA LAid 6 • • • • •0 P
H
P CM CM CM A A 00CM
00CM
H i-"
Id 0 P id 0 p p p Jd
I B gP Iu P p
O 0Ü s
«•H
Id d P A P
^ 0 8
Id■gd*P Ü
o
p
p0 id A 0
P <c
g
a
P o
II• s o0O
ON O CM(A o m
lAp 3
CO r— rA rA
II§ •
P
A
OON
r-rA
VOCO 3 CO
r -
COCM
rACO a rA
CMCOCM
COCO
CM P ON 00
§g§X
io
a
s0p
Igp
s<
ICM
LA lA
lALA
rAON
r - ONxt xt
r- VO LA hACM LA rA 00 LA
r it - j IK ^ - j — IK " I . . . . IK
IA
§■p0Üc
IdpÜ0u0
p
1B00g§Id000A
IdP0
idIS0
so■a0Ü
ê
PP PP 00 0
-f~ 0A P0 AP PO OP P0 0A APr AO O•H •HA AEH Eh
IK H"
55
VO
0P«Eh
* 0 •P P A H EH'--'
p + TJ 1 ib <D«-IH pp P O >> P 00 ü _ s o dA 0 id p p *HP p p 0 A pO P 0 8 ü pP O P 1 1 pO ü >H ^ O 0pAü 4h1 O 1 1O P O
1• 0 P P P
0 P 0 A P44 0 >H 8 0 PO P 1 1 P
O O 00 P
g0iA P - d . 1
P 0 44 OP ü P O P 0d p 0 O Pp p 0 id P Po 0 P p A P0 B P 0 0 P
0 O p 1 d0 P ü >3 o 0p 00N 4h 4hP O o 10 _ oA 0 id p 0
ü p o d4h P 0 p pO 0 p A p
0 JH 0 PP 0 1 PO P ^ O 0p Pp0 0
P A Aid0
P0C?
P P p üP p >H ,
•H 4-H0 o
S Po pp ü P4h O
P P0 te 0 id0 A 0P PlS
•H o idS p <50 A
Eh4hO
0idp0P>H
id
p o
II-S "0Ü
LA LA A A A ACM CM r- CM A A A A M CM
; • •CM CM p A CM CM CM CM P A
vom a
vo lA rA A-
OrA
ONP
a
IA§•NP0PQ
rAP
r-
s00 r -r- CM
ONMM r -00
o o vo LA LA
VO p LA A"
CM O ON LA
00rA
LA ON p
orA00 LA CM LA
CMP
VOVO rA CM CM
hA CTN M ON rA LA o LALA r - VO r - LA o vo
rH
îK ”f~ IK “4“ «K 4^ 4“ 4—
iI
:o
a
0P01—10APAP 0P i P0 OP PP 0>> AP P i0 O0 P< 01 0
CM <4
Ap ü 04h O
P
gG 0 0 P
0 X O
B 0 ü
g
gid
g0A
AP0X
PP
•3p
id0p
p00 0 0 0 A p0 A
g
^ sg- §•
p p
g g
îK -j—
56
w ere i n v e s t i g a t e d . The r e s u l t s a re shown i n T a b le s 3 - 6 .
o - G h lo r o a n i l in e was fo rm ed a s w e ll a s N-me th y 1 - o - c h i o r o a n i 1 i n e ,
from p h o to ly s e s in v o lv in g th e am ino a c i d ; th e y i e l d s o f b o th
o f th e s e p r o d u c ts a r e g iv e n i n T a b le 6 .
I n th e t a b l e s , th e *% y i e l d o f s u b s t i t u t e d h y d ro ca rb o n *
i s th e y i e l d a ssu m in g 100% d e c a r b o x y la t io n o f th e a c i d .
The im p o r ta n t f i g u r e s to n o te a r e th e * c o r r e c t e d y i e l d s o f
s u b s t i t u t e d h y d ro c a rb o n s * ; th e s e a r e b a s e d on th e a c t u a l
q u a n t i t y o f a c i d d e c a rb o x y la te d , a n d th u s , e f f e c t i v e l y g iv e a
m easure o f th e e f f i c i e n c y o f th e fo rm a t io n o f RXCHq , from
RXGHg * r a d i c a l s , by h y d ro g en a b s t r a c t i o n r e a c t i o n s I
RXGHq • + HY -h RXGHg + Y*
[w here *HY* i s a h y d ro g en d o n o r ] .
I n a l l c a s e s , th e y i e l d o f s u b s t i t u t e d h y d ro c a rb o n was
g r e a t e r f o r r e a c t i o n s c o n ta in g th io p h e n o l , i n d i c a t i n g t h a t
r a d i c a l s o f ty p e RXGHg * a r e in v o lv e d .
The p r o d u c t io n o f c a rb o n d io x id e p e r u n i t tim e was
a lw ay s lo w e r f o r r e a c t i o n s ru n i n th e p re s e n c e o f t h i o
p h e n o l , The a b s o r p t io n o f l i g h t by th io p h e n o l , a t 350 n m ,,
th e w a v e le n g th o f th e l i g h t u s e d i n th e s e i r r a d i a t i o n s , i s
n e g l i g i b l e , a n d h e n c e i t i s n o t a c t i n g a s an i n t e r n a l f i l t e r .
P h y s ic a l q u e n ch in g an d c h e m ic a l quenching^^of th e e x c i t e d
s t a t e s o f a ro m a tic k e to n e s , by th io p h e n o l , h a s b e e n o b s e rv e d ,
Gohen e t a l r e p o r t e d t h a t t h i o l s r e t a r d o r i n h i b i t th e
57
p h o to r e d u c t io n o f benzophenone i n p ro p a n - 2- o l ; th e m echanism
s u g g e s te d f o r th e t h io p h e n o l - i n h i b i t e d r e a c t i o n was a s
f o l lo w s I
PhaCO* + MegCHOH
Meg COH + PhSH
PhS* + PhgCOH
Pha COH + Meg COH
MeaCHOH + PhS*
PhSH + Pha CO
I t i s m ost p ro b a b le t h a t th e r e t a r d a t i o n o f th e d e c a r b o x y la t io n
r e a c t i o n s ,b y th io p h e n o l , i s a r e s u l t o f p h y s i c a l q u e n ch in g .
The p ro d u c t io n o f o - c h l o r o a n i l i n e , i n p h o to ly s e s in v o lv in g
IT-( o - c h lo r o p h e n y l )g ly c in e , p ro b a b ly o c c u rs v ia th e S c h i f f
b a s e . I , a s fo l lo w s I
NHCH.
Cl
NHCH2
O
Cl
N = C H ,
RgCOH
NH.
■>Cl
58
D e te rm in a t io n o f P ro d u c ts by Column C hrom atography
A r e p r e s e n t a t i v e p r o p o r t io n o f th e r e a c t i o n s w ere w orked
up by colum n c h ro m a to g ra p h y . The r e a c t i o n s i n v e s t i g a t e d
w ere th o s e o f benzophenone w ith p h e n o x y a c e t ic a c i d , (p h e n y l-
t h i o ) a c e t i c a c i d , and N - ( o - c h io r o p h e n y l )g l y c i n e , f lu o re n o n e
w ith N - ( o - c h lo r o p h e n y l ) g ly c in e , an d x a n th o n e w ith phenoxy
a c e t i c a c i d . P in a c o ls w ere p ro d u c e d i n good y i e l d , from th e
c o r r e s p o n d in g k e to n e s , i n a l l r e a c t i o n s e x c e p t w ith x a n th o n e -
p h e n o x y a c e t ic a c i d , i n w hich th e x an th o n e was r e c o v e re d i n
80% y i e l d . T a rs w ere p ro d u c e d i n a l l th e r e a c t i o n s . The
o th e r p r o d u c t s i s o l a t e d w ere s u b s t i t u t e d h y d ro c a rb o n s , c a rb o n
d io x id e , and th e s t a r t i n g k e to n e s . 1 ,2 - D ip h en o x y e th an e
was fo rm ed from r e a c t i o n s o f p h e n o x y a c e t ic a c id .
Summary o f P ro d u c t F o rm a tio n
The fo rm a t io n o f th e p r o d u c ts o b ta in e d may be r a t i o n a l i s e d
a s f o l lo w s !
R'aCO » • R 'aC O *
* , .R'aCO + RXGHgCOgH ------- > R'gCOH + RXC% ' + GOg
R'gCOH + RXGHg* ------ ». Rg'CO + RXGHg . . . . . . . . ( l )
2R 'a C 0H ». Ra'COH ( 2 )
Ra 'GOH
2RXGHg* ». (RXGHg )g ( 3 )
59
I t a p p e a r s t h a t d im é r i s a t i o n o f p r o to n a te d k e t y l r a d i c a l s , ̂ Ce> <̂xr oj)
R*gCOH, ( e q u a t io n ( 2 ) ) , i s favoursdy^^to t h e i r r e a c t i o n w ith
RXGHg • r a d i c a l s ( e q u a t io n ( 1,)); h e n c e , th e RXGHg * r a d i c a l s
u n d e rg o o th e r r e a c t i o n s , su ch a s d im é r i s a t i o n ( e q u a t io n (3 ) ) ,
e . g . fo r m a t io n o f 1 , 2-d ip h e n o x y e th a n e from p h o to ly s e s
in v o lv in g p h e n o x y a c e t ic a c i d . A l t e r n a t i v e l y , an d w hat i s more
l i k e l y , th e RXGHg * r a d i c a l s a t t a c k th e s o lv e n t b enzene to
i n i t i a t e a c h a in r e a c t i o n , from w hich p o ly m e r ic p r o d u c ts a re
o b ta in e d ( e q u a t io n (4 ) ) I
RXCH RXCH
RXCH,
etc. (4 )
P r o d u c t io n o f p o ly m e rs , i n t h i s way, c o u ld a c c o u n t f o r
th e t a r s p ro d u c e d i n th e r e a c t i o n s , and a l s o f o r th e re c o v e ry
o f low y i e l d s ( < 50^ ) o f p r o d u c t s d e r iv e d from th e a c i d ,
c . f . > 80^ re c o v e ry o f p r o d u c ts d e r iv e d from th e k e to n e .
I t i s i n t e r e s t i n g to n o te t h a t s t a b l e a d d u c ts , 1 1 , a r e
n o t fo rm ed i n th e s e r e a c t i o n s !
OH- * I ‘
i . e . Rg*GGH + RXGHg* R*gG-GHgXR
11
60
The f a c t t h a t f lu o re n o n e an d 2 - a c e ty ln a p h th a le n e can
b r in g a b o u t th e d e c a rb o x y la t io n r e a c t i o n s i s w o rth y o f n o t e .g
M ost a ro m a t ic k e to n e s have a n , i r c o n f i g u r a t i o n i n t h e i r
lo w e s t e x c i t e d t r i p l e t s t a t e s ; h o w ev er, f lu o re n o n e and
2 -a c e ty ln a p h th a le n e have a Tr,ir* c o n f i g u r a t i o n . As a
r e s u l t , th e p h o to c h e m is try o f th e l a t t e r k e to n e s i s d i f f e r e n t
to o t h e r a ro m a tic k e to n e s . The t t , i t s t a t e o f th e c a rb o n y l
g roup i s o f t e n u n r e a c t iv e i n p h o to c h e m ic a l r e a c t i o n s ; f o r
ex am p le , f lu o re n o n e and 2- a c e ty ln a p h th a le n e a r e p h o to re d u c e d74 ̂75
v e ry i n e f f i c i e n t l y by a lc o h o ls ' (w h e rea s k e to n e s w ith a
n ,ir* t r i p l e t s t a t e a r e p h o to re d u c e d e f f i c i e n t l y e . g .7 76
p h o to r e d u c t io n o f benzophenone by b e n z h y d ro l , p ro p a n - 2- o l ,
e t c . ) .A s a c o n se q u e n c e , i t seem s u n l i k e l y t h a t th e
d e c a r b o x y la t io n r e a c t i o n s o c c u r by i n i t i a l h y d ro g en a b s t r a c t i o n ,
i n th e f o l lo w in g way!
= 0 ^ i4 c - 6
RXGHg ̂ ^ RXGHg GOg
—CR ̂ + I^COH
RXGHg CO2 • ^ RXGHg * + GOg
The d e c a rb o x y la t io n may p ro c e e d , how ever, i f th e h y d ro g en
a b s t r a c t i o n p ro c e s s o c c u rs w ith c o n c e r te d l o s s o f c a rb o n
d io x id e . I n t h i s c a s e , th e f r e e e n e rg y o f fo rm a t io n o f
c a rb o n d io x id e , w hich i s l i b e r a t e d , may be s u f f i c i e n t to
f a c i l i t a t e th e d e c a r b o x y la t io n J
61
I . e .
. nRXGHg•
RXGHg—‘G p . . J + GO0 —H « 0 -GI^ 2
+ E^COH
2 .1 .3 P ro d u c t S tu d ie s f o r R e a c t io n s In v o lv in p : Q u in o n es ,
Y ie ld s o f S u b s t i t u t e d H y d ro ca rb o n s
The y i e l d s o f s u b s t i t u t e d h y d ro c a rb o n s , from i r r a d i a t i o n
(p ro c e d u re B - s e e s e c t i o n 2 .2 ) o f b en zen e s o l u t i o n s o f
c a r b o x y l ic a c i d s , c o n ta in in g q u in o n e s , i n th e p re s e n c e and
a b se n c e o f th io p h e n o l , w ere d e te rm in e d by g a s - l i q u i d
c h ro m a to g ra p h y . The d e c a r b o x y la t io n s o f p h e h o x y a c e t ic a c i d ,
( p h e n y l t h i o ) a c e t i c a c i d , S - ( n - b u t y l t h i o ) a c e t i c a c i d , a n d
N - ( o - c h lo r o p h e n y l ) g ly c in e s e n s i t i s e d by 9 , 10- a n th r a q u in o n e ,
9 , 10-p h e n a n th r a q u in o n e , and te t r a c h lo ro - p - b e n z o q u in o n e w ere
i n v e s t i g a t e d . The r e s u l t s a r e shown i n T a b le s 7 -1 0 . The
y i e l d s o f o - c h l o r o a n i l i n e a r e in c lu d e d i n T a b le 1 0 .
The r e s u l t s a r e s i m i l a r to th o s e o b ta in e d w ith th e
k e to n e s i n t h a t th e y i e l d s o f s u b s t i t u t e d h y d ro c a rb o n s w ere
i n c r e a s e d on a d d i t i o n o f th io p h e n o l , w h ich a l s o c a u se d a
r e t a r d a t i o n i n th e r a t e o f c a rb o n d io x id e p r o d u c t io n ; th e
same a rg u m e n ts a p p ly a s u se d f o r th e r e a c t io n s in v o lv in g
k e to n e s , ( s e e s e c t i o n 2 . 1 . 2 ) . W ith 9 , 10 -a n th r a q u in o n e , v e ry
62
d•rH
'd•Hü0
ü•H•P0ü
aXod0XîP«HO
0do•H-Pd(HO •0 0
00 dd o0 dN •Hd d0 arû
<d<+H OO
0d üo d•H 0■P 00 0
•H d"d P0d 0d XI•H ■P
eod<u
01—1o0•Hd0uo0'drH0•H
0rH
0EH
§ â+3CO 0 •H S nd *H CO Eh
H
^ r 0 <tH +5 0 0^ -d O
rH ro
O -H *3 ü >a 0
S
0
Td 0 iH •rj 0 (h•H 0
O
*d N H o 0 ü •H>H <H
o
"30 »d
I Ir
mCM
8 8 rH rH
Om
Flr --d"
tri
0dod•Hd0dX+3
0 dd <o 1d o•H rHdcÿ Ch
r -rn
tK
I•H
g.Sg
#
IIo
os
mCM
Ch -d- -d- ^
ooI—I
tü
i•H
&0Ng1
O
0
1g
S
d00
0
I
&•H
g
*
•Pd00
gPiI—IOd
&•H
g
'd
0rH
&0
1Ü
'§
'd•Hü0
0
10
g
000
TjI—I 0
H t -
63
<+HO
0g
•H■PdrHO0
ë0d0rÛ
o
g•H-p0
3gd
e0
6«§•HXîP
1&
P
-P
e
%-S(—I 0
•H>H
00
0 I—I
I
0
§d•Hdü<+H00
d00
gA
1
rd•Hü0ü•H-P0ü0
0 •HXJ■PrH
1
g t: : p 50
•H 0Tj ag gd
M
4 P Td
rH 0>9^}
0 Pi
- '30 <fH 0
g s &d 0 0 O ‘H x;
ü >9 Pi
<8•H
"âH d
H -p H 0 0 ^
B d. 0 «H x îo A
H C ?0 ü
Td
>H OHo
0 'd x î 0
•H <C
g
§d
•H
â
oorH
O Ch O m rH
LTv 00m xJ-
MD m i n _d"
I•H
&ggd
oH
Ch
m
oCM
OCM
CM rH m Ml
lACM
iag.ggd
g
orH
Ch
A
r-A
i•H
&0Nd0X)1
g"go3üg+3
s
A
A A 'X) 'X) CM A
A A
* -I— W 4 — « - f -
■d
g0
Sog00
8Td•Hü0<HO•Pd
-P O-p d ad 0 00 00 0 d
p d o0 A
id1—1 rH 0O O 0d d 00 0 P
p PT)A A
O O rH•H •H 0P P •rHEH Eh >H
K 41-
64
<ÎHoCQ§•H+)0rHOCQ
§(D
Ü0
<HO
0•H<Pco•H
05hfH•H
es<H
>§•HX!
îrHS■p
§rH
1%
SI—I 0 ♦H>4
CTi
0rH
I
0
I•H
a
O
8g0
£Pt
■P
•H
•Hü0
ü•H•P0ü0
O•H
grH
Bh ,
44 -
u0•H 0Xi a0 *H
M
-S•Hxî
0 «tH 0■P O Hü >>rH 0 -P >s H rH JS XîP, 0 X)O «H I 0 Ü >5 Pl S
ë•H
â î
A4 0o a
0 ü •H^ Ah
O
rHOPi . 0 «d
IIr
§a•H
i^ r - Mm MD vo MO MO
CM CvJ x t -d- rH rH
0000
voCTv
vom
V£»
Shr -
*
I•H
&sga?orH
CT»
OCM
i•H
D*0(hXî■P0
II
OH
G\
m
*
i•H
&0Nd0X21
fgo
S-p
g
00rH
ndg0H
SS«»d•Hü0A4o■P
§a0
, -p 0■P p! Xîd 00 00 0X5 p, O0 A fdrH rH 0O O 0Pl d 00 0 PX! XIPM A •dO O rH•H •i4 0xî XI •HEh Eh
in +- 44-
65
iXIpodorHXIü
o—'1
s
AhO
0do•H-P 0d 0rH dO o0 d
•H0 dd a0N Ahd O0X 0
üAh dO 0
0d 0o d•H P-po 0•rH Xd -p0d dd •H•iH
0a do •Hd üAh >s
rH0 bC0d•Ha0
AhO
0drH0•H>4
OH
0rH
«Eh
-H -
• 0 •ph e ph Jh *H xî H E h ^
- H -
•d , I l
ü ^ o0 *d -p rH ^ H 0 Xî Pi 0 a ü O *H I Iü >slz; O
IrH
è ,PU 0o d
^ 3 M
^ o o 0
•HiHg0
+a0aI
"d0 Ah -P O ü
iPi 0 O d
0 d H *H b rH rH Pi 0 ü -H O «H I d O >& O 0
° id d 0 H o d0 rH iH H XÎ H >H ü -H
I ÜO 0
drH<D•H>4
( fÜ
AhO
•30 dXI 0
r
I•H
â
kO VO
o\ rHm
<M
m
m
r -in
oco
rH
CMrHrH
*
m
<y\
r -xj-
CTv CTi 0 0
m
Kl
m
xfrH
r -m
IK
0i•H
d do o<d o
0 •iH Nd d do o* 0d ? X•H d 1d XÎ A
■P 10 d Od 0 dXI d O•p 0 Hd X 2<Î A ü1 1 0
O O drH rH X
0en en Eh
CM
un 00 00r- m m
voI—I
CMxt d
00x>0
0 d
1•HXIE4
*
-PdSdA
II•H
g
d
0
If .0üëd•Hü0
AhO
0
1 gd000X
drH0•H>4
-H-
66
h ig h y i e l d s o f s u b s t i t u t e d h y d ro c a rb o n s were fo rm ed i n a l l
c a s e s , e x c e p t f o r th e r e a c t i o n w ith N - ( o - c h io r o p h e n y l ) g ly c in e .
T h is can be e x p la in e d by two a l t e r n a t i v e m echan ism s, w hich
a r e shown i n p a th w ay s ( i ) and ( i i ) I
RXCHgCOgH
+ RXCHg
IV OCHgXR+ RXCH3
The ’ se m iq u in o n e ' r a d i c a l . I I I , d o es n o t d im e r is e
e f f i c i e n t l y , i n c o n t r a s t to th e p r o to n a te d b e t y l r a d i c a l
o b ta in e d i n th e r e a c t i o n s o f th e a ro m a tic k e to n e s . Aa a
r e s u l t , h y d ro g en a b s t r a c t i o n , by th e RXCEj * r a d i c a l , c o u ld
become a v e ry fa v o u ra b le p r o c e s s g iv in g good y i e l d s o f
s u b s t i t u t e d h y d ro c a rb o n , RXCH3 , a s i n p a thw ay ( i ) .
A l t e r n a t i v e l y , an a d d u c t , IV , c o u ld be fo rm ed a s i n pa thw ay
( i i ) , A d d u c ts o f t h i s ty p e have n o t b e e n r e p o r t e d i n th e
l i t e r a t u r e , p ro b a b ly due to r a p id d i s p r o p o r t i o n a t i o n , a s
shown; t h i s c o u ld a l s o a c c o u n t f o r th e h ig h y i e l d s o f RXCH3,
The y i e l d s o f s u b s t i t u t e d h y d ro c a rb o n s , from r e a c t i o n s
in v o lv in g te t r a c h lo ro - p - b e n z o q u in o n e a n d 9 , 10 -p h e n a n th ra q u in o n e
w ere , i n many c a s e s , l e s s th a n lO^o, i n th e a b se n c e o f
67
th io p h e n o l* Q uinones a r e n o ta b le s c a v e n g e rs o f r a d i c a l s
and i n th e s e c a s e s i t i s l i k e l y t h a t a d d u c ts , o f ty p e
V, a r e b e in g form ed*
77
0 RXCHgCOgH -CO2HO
HO
A d d u c ts w ere so u g h t a f t e r f o r r e a c t i o n s in v o lv in g
c h l o r a n i l ( s e e l a t e r ) .
Prom T ab le 1 0 , o - c h l o r o a n i l i n e , a s w e l l a s N -m e th y l-o -
c h l o r o a n i l i n e , i s fo rm ed from p h o to ly s e s in v o lv in g
N - ( o - c h lo r o p h e n y l) g ly c in e , c . f . T a b le 6 . W ith th e qu in o n e
r e a c t i o n s th e r e a r e two p o s s ib l e p a th w ay s to t h i s p r o d u c t ,
i . e . v ia a n a d d u c t (pa thw ay ( i i i ) ) , o r v ia a S c h i f f b a se
(pathw ay ( i v ) ) :
OH
OHNHCH-
OHOH
CH,0OH
68
D e te rm in a t io n o f P ro d u c ts by Column C hrom atography
The r e a c t i o n s of* t e t r a c h lo ro - p - b e n z o q u in o n e w ith
p h e n o x y a c e t ic a c i d , ( p h e n y l t h i o ) a c e t i c a c id , and N - ( o - c h lo r o -
p h e n y l )g ly c in e , and a n th ra q u in o n e w ith p h e n o x y a c e t ic a c id and
( p h e n y l t h i o ) a c e t i c a c i d , were i n v e s t i g a t e d by colum n ch rom ato
g ra p h y . Q u a n t i t a t i v e re c o v e ry o f a n th ra q u in o n e was
o b ta in e d f o r r e a c t i o n s in v o lv in g t h i s q u in o n e ; t h i s w ould be
e x p e c te d on th e b a s i s o f th e m echanism s d i s c u s s e d i n th e
p r e v io u s s e c t i o n , T e tr a c h lo ro -p -b e n z o q u in o n e was fo u n d to
g iv e th e a d d u c ts 0 - ( phenoxym ethy1 ) - 2 , 3 , 5 , 6- t e t r a c h i o r o q u i n o l ,
V I, an d O“ ( p b e n y l th io m e th y l ) - 2 ,3 ,5 , 6- t e t r a c h l o r o q u i n o l , V I I ,
from i t s r e a c t i o n s w ith p h e n o x y a c e tic . a c i d and ( p h e n y th io ) -
a c e t i c a c i d , r e s p e c t iv e ly !
o o
Yi YÜ
The e x i s te n c e o f th e s e a d d u c ts c o r r e l a t e s w ith th e v e ry
low y i e l d s o f s u b s t i t u t e d h y d ro c a rb o n s o b ta in e d w ith th e s e
a c id s ( s e e T a b le s ? and 8 ) , No a d d u c t was i s o l a t e d from th e
r e a c t i o n o f t e t r a c h lo ro - p - b e n z o q u in o n e w ith N - ( o - c h lo r o -
p h e n y l )g ly c in e ; t h i s i s i n good a g re e m e n t w ith th e f a i r l y
h ig h y i e l d o f o - c h l o r o a n i l i n e o b ta in e d from t h i s r e a c t i o n
( s e e T a b le 1 0 ) ,
69
2 .1 .4
Summary o f P ro d u c t F o rm a tio n
The d i f f e r e n c e s b e tw een th e p ro d u c ts o b ta in e d from
k e to n e and qu inone r e a c t i o n s can b e e x p la in e d i n th e fo l lo w in g
way. The p r o to n a te d k e t y l r a d i c a l s , R3COH, p ro d u c e d in
r e a c t i o n s o f k e to n e s , d im e r is e e f f i c i e n t l y , w h ereas th e
sem iq u in o n e r a d i c a l s , p ro d u c e d i n r e a c t i o n s o f q u in o n e s , do
n o t d im e r is e . H ence, a d d u c t f o rm a t io n i s f a c i l i t a t e d w i th
th e sem iq u in o n e r a d i c a l s , e . g . w ith t e t r a c h lo r o - p - b e n z o q u in o n e ;
i n th o se c a s e s i n w hich h y d ro g en a b s t r a c t i o n , by RXCHg*, i s
more f a v o u r a b le th a n a d d u c t fo rm a t io n , e . g . w ith a n th r a q u in o n e ,
h ig h y i e l d s o f s u b s t i t u t e d h y d ro c a rb o n s a r e o b ta in e d .
70
2 .1 .5 M e c h a n i s t i c S t u d i e s
K i n e t i c s o f th e D e c a r b o x y la t io n R e a c t i o n s .
The a b s o l u t e r a t e c o n s t a n t o f a p h o to c h e m ic a l r e a c t i o n
can o f t e n g iv e i n f o r m a t i o n a b o u t th e mechanism o f th e
r e a c t i o n . I n th e c a se o f th e d e c a r b o x y l a t i o n r e a c t i o n s ,
t h e r a t e c o n s t a n t f o r d e c a r b o x y l a t i o n (k^ ) c a n n o t b e d e t e r
m ined from th e s im p le S t e r n Volm er e q u a t i o n [ ] , a s i t i s
p r o b a b le t h a t t h e c a rb o n d io x id e i s n o t e v o lv e d i n th e
p r im a ry p h o to c h e m ic a l r e a c t i o n .
1 k d7 = 1 + ...... ................ .....................
(where * ^ * i s th e quantum y i e l d f o r f o r m a t io n o f c a rb o n
d i o x i d e , i n th e a b se n c e o f q u e n c h e rs , *k^’ i s a c o m p o s ite
r a t e c o n s t a n t f o r d e a c t i v a t i o n o f th e e x c i t e d s t a t e o f t h e
s e n s i t i s e r (by r a d i a t i v e and n o n - r a d i a t i v e p r o c e s s e s ) ,
and i s th e i n i t i a l c o n c e n t r a t i o n o f t h e a c i d ) .
The k i n e t i c scheme p ro p o s e d f o r t h e d e c a r b o x y l a t i o n
r e a c t i o n s i s shown on p ag e 71 . I t i s p ro p o s e d t h a t t h e
r a t e - d e t e r m i n i n g s t e p , f o r t h e d e c a r b o x y l a t i o n , i s s t e p ( 3 ) ,
i . e . t h e f o r m a t io n o f an i n t e r m e d i a t e com plex by r e a c t i o n o f
a m o le c u le o f t h e s e n s i t i s e r , i n i t s f i r s t e x c i t e d t r i p l e t
s t a t e , w i th a m o lecu le o f t h e a c i d , i n i t s g ro u n d s t a t e .
71
P ro p o s e d K i n e t i c Scheme f o r D e c a r b o x y la t io n o f C a r b o x y l i c
A c id s i n th e P re s e n c e o f C a rb o n y l Compounds.
R a teh^
^ so
K^I
c . A
Krjyj + Q
Kgi > K^j ....... I
^SO .......( 2 )k^
— ^ C .......(3 )
5 ̂ COg - . . . . ( 4 ) k c o / C ]
^ so + ^ ....... (5 ) k^ [C ]
* -..(6 ) k q [ K ^ l ] [ e ]
(w h e re , *Kgg' i s t h e s e n s i t i s e r i n i t s g round s t a t e ,
*K si ' i s th e s e n s i t i s e r i n i t s f i r s t e x c i t e d s i n g l e t
s t a t e .
^K^I* i s th e s e n s i t i s e r i n i t s f i r s t e x c i t e d t r i p l e t
s t a t e .
i s t h e a c i d i n i t s g ro u n d s t a t e ,
i s th e q u e n ch e r i n i t s g round s t a t e ,
*0^ 2 * Î 8 th e q u e n ch e r i n i t s f i r s t e x c i t e d t r i p l e t
s t a t e ,
*C* i s a com plex ,
*1 * i s t h e l i g h t i n t e n s i t y ,
' i s th e r a t e c o n s t a n t f o r f o r m a t io n o f c a rb o nCUgd io x id e from t h e com plex ,
*k^* i s t h e r a t e c o n s t a n t f o r d e a c t i v a t i o n o f t h e
com plex , t o g iv e g ro u n d s t a t e r e a c t a n t s ,
and *kq' i s th e r a t e c o n s t a n t f o r q u e n ch in g by Q ).
72
Quantum y i e l d f o r d e c a r b o x y l a t i o n , = N, ^ , i n th e
p r e s e n c e o f q u e n c h e rs , (where 'N ' i s th e f r a c t i o n o f
t r i p l e t s , o f th e com plex , w hich r e a c t t o g iv e c a rb o n d i o x id e ,
and ' ^ ^ i s th e quantum y i e l d o f com plex f o r m a t i o n ) .
U nder s t e a d y s t a t e c o n d i t i o n s !
I = k ^ [ K ^ j ] [ A ] + k ^ [ K ^ j ] + kq [ K j j ] [ Q ]
N k . + kq[Q]. , —— = 1 + ——— — ——
q k^[A ]
However, i n th e a b se n c e o f q u e n c h e rs ;
^ k^[A]
d) _ kq[Q]— — % « . . . « .
S in c e a r a t i o o f quantum y i e l d s i s i n v o lv e d , th e a c t u a l
w e ig h ts o f b a riu m c a r b o n a te , p ro d u c e d i n t h e quenched and
u n q u en ch ed r e a c t i o n s , can be u t i l i s e d . H ence, e q u a t io n
73
becomes I
[BaCOg ]unqu _ kq[Q]-------------------- “ 1 + (wO
[BaCOg ]qu k^[A ] + k ^
(where * [BaCOg ]unqu* i s th e w e ig h t o f b a r iu m c a r b o n a te from
th e u n q u en ch ed r e a c t i o n i . e . c o n s t a n t , and * [BaCOg ]qu* i s
th e w e ig h t o f b a r iu m c a r b o n a te from th e quenched r e a c t i o n
i . e . v a r i a b l e ) .
H ence, a p l o t o f [BaCOg]unqu v e r s u s [ q ]
[BaCOg ]qu
w i l l g iv e a s t r a i g h t l i n e o f s lo p e kq .
A l l th e f a c t o r s a r e known, e x c e p t k ^ , w hich can t h e r e f o r e be
o b t a i n e d .
Oxygen Q uenching S t u d i e s
P r e l im i n a r y s t u d i e s , u s i n g oxygen a s th e q u e n c h e r , were
c o n d u c te d i n o r d e r t o e s t a b l i s h a p p ro x im a te v a l u e s f o r th e
r a t e c o n s t a n t s o f d e c a r b o x y l a t i o n . The y i e l d s o f c a rb o n
d i o x id e from th e d e c a r b o x y l a t i o n o f b en zen e s o l u t i o n s o f
p h e n o x y a c e t ic a c i d , ( p h e m y l th ic ja c e t ic a c i d , S - ( n - b u t y l t h i o ) -
a c e t i c a c i d , and N - ( o - c h l o r o p h e n y l ) g l y c i n e , s e n s i t i s e d by
benzophenone and t e t r a c h l o r o - p - b e n z o q u i n o n e , i n th e p r e s e n c e
o f n i t r o g e n and oxygen, a r e shown i n T a b le 11 .
74
d d0 o ♦H
1 d •H aO o P 'w 'tsj d 0
1 d •H •rH 0d 0 d a0) m C?i 0 •rHbC O d Eh>? <H N dX o d H
O 00 p
'd ü 1 0d d p^ Aco 0 1 •iH
0 o Xd 0 d od) o *d •iHbC A H rH AO P 0^4 0 ü •rH d■P x : 0 >H o•iH p d p
P dd 0 0
An •H Eh ÜO
0X 'd
d •H d •o ü o d
•H •H pP p aCO ü 0
•iH ♦H •H'd 1—1 » ' »d 0CD >? 0 0 a1h K d d •HJh o o d EhH XI d M
d •Ha 0 do O a 0u O 'du <P N p
O d X(D 0 o
0 X 0 •d •rH•H d 1 d 1—1 AX o p g 0o •H 1 d •H d•H P o 0 oA d d P P
iH o p dd O rH o 0o CQ Xî tq Ü
rO O dd 0 0 0co d d A "d
ü 0 P 0N 0 0
<H d Eh AO 0
A 'd 0—> d 0
'd 0 CÎJ0
p 0(0 0 dT) d oiH d d0 p 0
•H 0 XI>H 0 P
(DrH
«Eh
I—I H
m (M m vo
CNJ CMMl
i—ICM
s"
rd•Hü(0ü•H■P
8
&0Ü
1
m m Ul Ulm Ul m m
vû vX) m r-
s" c?
nj•HüCOü
•H•P
8CO
o•H
g
HMl CM-d*
M l dCM
ij•HüCO
ü•H■P
8CO
0 •H
grH
1I
CQ
-d* -d"
c?
mCM R
LCl rHm rH
CM
c?
8•Hü>>
M
tIO
a?o
"d(Dcod
I(DüO
&
g•H■PCO•rH'dg
75
The r e a c t i o n s s e n s i t i s e d by benzophenone were r e t a r d e d
by o x y g en ; how ever, th e f a c t t h a t some d e c a r b o x y l a t i o n was
o b s e r v e d i n d i c a t e s t h a t t h e t r i p l e t s t a t e , o f th e b en zo p h en o n e ,
r e a c t s v e r y e f f i c i e n t l y w i th th e a c i d s . A pp ro x im ate r a t e
c o n s t a n t s f o r th e r e a c t i o n s o f benzophenone w i th ( p h e n y l t h i o ) -
a c e t i c a c i d , S - ( n - b u t y l t h i o * ) a c e t i c a c i d , and N - ( o - c h l o r o -
p h e n y l ) g l y c i n e were o b t a i n e d , u s i n g e q u a t i o n ( hi ) , a s su m in g
th e f o l l o w i n g d a t a , an d th e v a lu e s a r e shown i n T a b le 12!
[Q] = 9*3 X 10 ( s i n c e th e s o l u b i l i t y o f oxygen i n b e n z e n e ,
a t 25° , i s 0 .2 0 7 9 m l. oxygen p e r m l. b e n z e n e ) .9 w - 1 ______“1 79k q = 1 X 10 M . s e c .
^dk^ = 3 X 1 0 ^ s e c . ^
[A] = 3 .1 X
T a b le 12 A pp ro x im ate V a lu e s o f R a te C o n s ta n t s f o r
D e c a r b o x y la t io n o f C a r b o x y l i c A c id s , i n
Benzene S o l u t i o n . S e n s i t i s e d by Benzophenone
( from Oxygen Q uenching S t u d i e s . )
A c id k^ (M \ s e c .
N - ( o - C h lo r o p h e n y l )g l y c i n e 2 .0 x 10^Q
8- ( n - B u t y l t h i o ) a c e t i c 5 .0 x 10
( P h e n y l t h i o ) a c e t i c 1 . 4 x 10^
From T a b le 11 i t can be s e e n t h a t th e y i e l d s o f c a rb o n d i o x i d e ,
from r e a c t i o n s s e n s i t i s e d by t e t r a c h l o r o - p - b e n z o q u i n o n e ,
o b t a i n e d i n th e p r e s e n c e o f oxygen w e re , i n a l l c a s e s ,
g r e a t e r t h a n f o r th e c o r r e s p o n d in g r e a c t i o n s u n d e r n i t r o g e n .
The d é c a r b o x y l a t i o n r e a c t i o n s a r e n o t s e n s i t i s e d by oxygen
76
and an a l t e r n a t i v e e x p l a n a t i o n was s o u g h t a f t e r .
S t u d i e s w ere c a r r i e d o u t t o d e te r m in e t h e c o n c e n t r a t i o n
o f q u in o n e , i n th e r e a c t i o n m ix t u r e s , a f t e r i r r a d i a t i o n .
The p r o d u c t s o l u t i o n s from th e d e c a r b o x y l a t i o n o f phenoxy
a c e t i c a c i d and S - ( n - b u t y l t h i o ) a c e t i c a c i d were exam ined by
i n f r a r e d s p e c t r o s c o p y , th e r e a c t i o n s b e in g c a r r i e d o u t i n
t h e p r e s e n c e a n d a b sen c e o f ox ygen . The r e s u l t s showed t h a t
a s u b s t a n t i a l amount o f th e q u in o n e h a d b e e n consum ed, i n
t h e r e a c t i o n u n d e r n i t r o g e n , c o n s i s t e n t w i th th e f o r m a t io n
o f a d d u c t s ( s e e S e c t io n 2 . 1 . 3 ) ; how ever , l i t t l e o f th e
qu in o n e h a d b e e n u s e d up , i n th e p r e s e n c e o f oxygen, t h i s
b e in g p r o b a b ly due t o r e g e n e r a t i o n from th e se m iq u in o n e , a s
f o l lo w s !
HO 0* + O5
HO O* - h RXCHg
H-cOg
+ HO,
T h e r e f o r e , a s r e a c t i o n p r o c e e d s , th e c o n c e n t r a t i o n o f qu inone
w i l l rem a in e f f e c t i v e l y c o n s t a n t , i n t h e r e a c t i o n s u n d e r
oxygen , w hereas i t w i l l d e c r e a s e , i n th o s e u n d e r n i t r o g e n ;
a s a r e s u l t , i n th e fo rm e r c a s e more q u in one i s a v a i l a b l e
f o r r e a c t i o n , o v e r a g iv e n p e r i o d o f t im e w hich w i l l r e s u l t
77
i n s l i g h t l y h i g h e r c a rb o n d io x id e y i e l d s , a s i s fo u n d .
The r e s u l t s i n d i c a t e t h a t t h e r a t e c o n s t a n t s f o r th e
d e c a r b o x y l a t i o n r e a c t i o n s s e n s i t i s e d by q u in o n e s a r e v e ry
h ig h , a s th e r e a c t i o n c an compete e f f e c t i v e l y w i th q u e n ch in g
o f th e qu inone by oxygen . The r e g e n e r a t i o n o f th e qu in o n e
by oxygen p r e c l u d e s th e d e t e r m i n a t i o n o f th e r a t e c o n s t a n t s ,
i n t h e s e r e a c t i o n s , and an a l t e r n a t i v e q u e n c h e r , 9 - n i t r o a n t h -
r a c e n e , m ust be u s e d ( s e e l a t e r ) .
N a p h th a le n e Quenching S t u d i e s
The v a lu e s o f th e r a t e c o n s t a n t s f o r d e c a r b o x y l a t i o n ,
o b t a i n e d from oxygen q u e n ch in g s t u d i e s , a r e a p p ro x im a te , a s
o n ly one c o n c e n t r a t i o n o f th e q u e n ch e r c o u ld be t a k e n , t h i s
i t s e l f b e in g an e s t i m a t e . I n o r d e r t o o b t a i n a c c u r a t e
v a l u e s , f u r t h e r q u en ch in g s t u d i e s were c o n d u c te d . The
d e c a r b o x y l a t i o n r e a c t i o n s s e n s i t i s e d by benzophenone were
t a k e n a s b e in g r e p r e s e n t a t i v e o f th e d e c a r b o x y l a t i o n r e a c t i o n s
o f a ro m a t i c k e to n e s , i n g e n e r a l . The r a t e c o n s t a n t s f o r
t h e d e c a r b o x y l a t i o n o f p h e n o x y a c e t ic a c i d , S - ( n - b u t y l t h i o ) -
a c e t i c a c i d , ( p h e n y l t h i o ) a c e t i c a c i d , a n d N - ( o - c h lo r o p h e n y l )-
- g l y c i n e , s e n s i t i s e d by ben zo p h en o n e , w ere d e te rm in e d u s i n g
n a p h th a le n e q u e n c h in g . The k^ v a l u e s , o b t a i n e d from p l o t s
o f [BaCOg]unqu v e r s u s n a p h th a le n e c o n c e n t r a t i o n , a r e
[BaCOg ] qu
shown i n T ab le 1 3 .
78
T a b le 13 R ate C o n s t a n t s f o r t h e B e n z o p h e n o n e - S e n s i t i s e d
D e c a r b o x y la t io n o f C a r b o x y l i c A c id s , from
N a p h th a len e Q uench ing S t u d i e s .
A c id S o lv e n t (M \ s e c . ”^ )
P h e n o x y a c e t i c B enzene 1 ,7 x 10^Q
(P h e n y l t h i o ) ace t i c B enzene 1 ,0 x 10
( P h e n y l t h i o ) a c e t i c A c e t o n i t r i l e 1 .4 5 x 10^g
8- ( n - B u t y l t h i o ) a c e t i c B enzene 1 . 6 x 10
N -(o -C h lo ro p h e n y 1 ) g ly c in e A c e t o n i t r i l e 2 .1 x 10^
* B a se d on a v a lu e o f kq = 5 x 10^ M \ s e c , ^
The Mechanism o f D e c a r b o x y la t io n o f C a r b o x y l i c A c id s
S e n s i t i s e d by A ro m a tic K e to n es
The q uen ch in g o f t r i p l e t benzophenone by s u l p h i d e s and
am ines h a s b e en i n v e s t i g a t e d by Cohen and h i s c o w o r k e r s .
T h e i r r e s u l t s a r e g iv e n i n T a b le l 4 .
T a b le l 4 R a te C o n s ta n t s f o r th e Q uenching o f T r i p l e t Benzo
phenone by S u lp h id e s and Amines
Q uencher S o lv e n t kq (M \ s e c . ^ )
70 7M ethy l p h e n y l s u lp h id e Benzene 7 .5 x 10
gD i - n - b u t y l sulphide^® B enzene 6 .6 x 10
83- 9N ,N - D im e th y la n i l in e Benzene 2 .7 x 10
79
M echanism s, i n v o lv i n g an e l e c t r o n t r a n s f e r i n t h e r a t e
d e te r m in in g s t e p , have b e e n p r o p o s e d f o r th e q u e n ch in g o f th e
t r i p l e t s t a t e o f a r o m a t i c k e to n e s by s u l p h i d e s a n d 81 ,83 , 84 , 85
am ines . An e x c i t e d com plex i s fo rm ed w hich can
u n d e rg o e i t h e r d e a c t i v a t i o n t o th e g ro u n d s t a t e m o le c u le s
( v i a * b a c k - e l e c t r o n t r a n s f e r ’ ) , a s d e p i c t e d i n pa thw ay ( i ) ,
o r a p r o t o n t r a n s f e r r e a c t i o n , g i v i n g r a d i c a l s a s i n pa thw ay
( i i ) . [These p r o c e s s e s a r e e x e m p l i f i e d by th e q u e n ch in g o f
th e e x c i t e d s t a t e o f k e to n e s by a m in es , a s f o l l o w s ] !
+ N(CHaR): e l e c t r o nt r a n s f e r
•H
(RCHs )gN
A rg CQSO
A r , C - 0 j
(RCHg )2NCHR
+ A ro COH
A co m p a r iso n o f th e v a lu e s shown i n T a b le s 13 and 14 shows t h a t
th e r a t e c o n s t a n t s f o r q u e n ch in g a r e o f th e same o r d e r a s
th o s e f o r t h e a n a lo g o u s d e c a r b o x y l a t i o n r e a c t i o n s . H ence,
i t a p p e a r s l i k e l y t h a t a m echanism , i n which e l e c t r o n t r a n s f e r
i s i n v o lv e d i n th e r a t e d e te r m in in g s t e p , i s a l s o o p e r a t i n g
i n th e d e c a r b o x y l a t i o n r e a c t i o n s , a s f o l l o w s !
80
e . g .
ArgCO^j + RgNCHgCOgHe l e c t r o n
^t r a n s f e r
jirsCOgo
+ RgNCHgCOgH
+RgNCHgÔ
AroC5 -y j c ;oH
EgNCHg + COg
+ Aro COH
A s i m i l a r mechanism can be w r i t t e n f o r r e a c t i o n s i n v o lv i n g
th e o t h e r a c i d s . The o r d e r o f r e a c t i v i t y o f th e a c i d s
( i . e . amino a c i d s ^ s u lp h u r a c i d s ^ p h e n o x y a c e t ic a c i d ) i s
t h a t e x p e c te d from a c o n s i d e r a t i o n o f th e i o n i s a t i o n p o t e n t i a l s
o f th e r e l a t e d compounds! a n i s o l e , 8 .2 e.v.*® ; m eth y l p h e n y l
s u l p h i d e , 7 .9 e .v f ^ N - m e t h y l a n i l i n e , 7 .5 8 e.v.®^ . (The
i o n i s a t i o n p o t e n t i a l s f o r t h e a c i d s th e m s e lv e s have n o t b e e n
d e te r m in e d ) . I t was a l s o fo u n d t h a t g lyc ine** and iPrOCHgCOgH 88
v;ere n o t d e c a r b o x y l a te d ; t h i s i s p r o b a b ly due to t h e i r
h ig h i o n i s a t i o n p o t e n t i a l s ( ^ 9 e . v . ) .
D e te r m in a t io n o f Quantum Y i e ld s o f Carbon D io x id e f o r
R e a c t io n s S e n s i t i s e d by Benzophenone
The l i g h t i n t e n s i t y . I , u s e d i n a l l t h e d e c a r b o x y l a t i o n
r e a c t i o n s , s e n s i t i s e d by benzophenone ( i n d e t e r m i n a t i o n o f
r a t e c o n s t a n t s by n a p h th a le n e q u e n c h in g ) , was d e te r m in e d ,
u s i n g b e n z o p h e n o n e -b e n z h y d ro l a c t i n o m e t r y , ( s e e S e c t i o n 2 . 2 . 9 ) ,9
a s b e in g 3 .0 2 8 x 10 q u a n ta /1 i t r e / s e c , . . The quantum y i e l d s
f o r th e r e a c t i o n s a r e shown i n T a b le 1 5 .
61
T a b le 15 Quantum Y ie ld s o f C arbon D io x id e from D ecarboxy
l a t i o n o f A c id s S e n s i t i s e d by B enzophenone .
A c id
P h e n o x y a c e t ic
(P h e n y l th i o )a ce t i c
( P h e n y l t h i o ) a c e t i c
S - ( n-B u t y 1 t h i <5-
a c e t i c
N - ( o - C h lo r o p h e n y l ) -
g l y c i n e
S o lv e n t Mols.BaCQgp e r l i t r e p e r s e c . ( x 10"”̂ ®)
Benzene
Benzene
Benzene
3 .3 3
1 0 .1 2
A c e t o n i t r i l e 8 .4 8
8.78
A c e t o n i t r i l e 8 .4 8
Quantum Y ie ld o f COg E v o lu t i o n
0.11
0 .3 7
0 .2 8
0 .2 9
0 . 2 8
The v a lu e s o b t a i n e d i n d i c a t e t h a t d e c a r b o x y l a t i o n i s a
v e ry i n e f f i c i e n t p r o c e s s ( c o n s i d e r i n g t h e h ig h k r v a l u e s )
com pared t o , s a y , t h e p h o t o r e d u c t i o n o f a r o m a t i c k e to n e s by
a l c o h o l s e . g . t h e p h o t o r e d u c t i o n o f b enzophenone by b e n z h y d ro 1
h a s a quantum y i e l d ^ o f 0 .2 6 b u t a k r v a lu e o f o n ly 5 .0 x 1 0 ^-1 -1 -7M s e c . • . T h is i n d i c a t e s t h a t c h a rg e d e s t r u c t i o n , w i th
q u e n c h in g o f t r i p l e t ben zo p h en o n e , a s d e p i c t e d i n pa thw ay
( i ) , i s a v e ry e f f i c i e n t d e a c t i v a t i o n p r o c e s s .
An i n t e r e s t i n g f e a t u r e o f t h e s e r e s u l t s i s t h a t t h e
quantum y i e l d f o r th e d e c a r b o x y l a t i o n o f ( p h e n y l t h i o ) a c e t i c
a c i d i s lo w e r f o r r e a c t i o n i n a c e t o n i t r i l e s o l u t i o n t h a n f o r
r e a c t i o n i n ben zene s o l u t i o n . The r e s u l t s shown i n T ab le
1 3 , how ever, i n d i c a t e t h a t th e r a t e c o n s t a n t s f o r d e c a rb o x y
l a t i o n , i n t h e s e s o l v e n t s ,a re o f t h e same o r d e r . T h is
82
a p p a r e n t anom aly can be e x p l a i n e d a f t e r a c o n s i d e r a t i o n o f
th e r e a c t i o n m echanism . I t h a s b e e n p ro p o s e d t h a t r e a c t i o n
p r o c e e d s v i a th e u n d i s s o c i a t e d a c i d . I n benzene s o l u t i o n
t h e a c i d i s , t o a l l i n t e n t s and p u r p o s e s , a lm o s t c o m p le te ly
u n d i s s o c i a t e d , and t h e r e f o r e a v a i l a b l e f o r r e a c t i o n ; ho w ever,
i t i s l i k e l y t h a t i n a c e t o n i t r i l e s o l u t i o n (w hich h a s a
d i e l e c t r i c c o n s t a n t o f 3 4 .6 com pared t o 2 .3 f o r b e n z e n e )
t h e r e i s a p p r e c i a b l e d i s s o c i a t i o n . H ence, th e ’ ’ e f f e c t i v e
c o n c e n t r a t i o n * * o f u n d i s s o c i a t e d a c i d w i l l be l e s s i n
a c e t o n i t r i l e s o l u t i o n , t h e r e f o r e th e quantum y i e l d o f c a rb o n
d io x id e f o r m a t io n w i l l be lo w e r , com pared t o r e a c t i o n i n
b e n z e n e s o l u t i o n .
O th e r Mechanisms
T h re e a l t e r n a t i v e m echanism s c an be r u l e d o u t on th e
b a s i s o f th e k i n e t i c d a t a . They a r e a s f o l lo w s !
(a ) V ia H ydrogen Atom A b s t r a c t i o n
A r g C — H — ^ Ar^ COH + RGOg
—COg
R*
The r e a c t i o n c o u ld a l s o p r o c e e d v i a c o n c e r t e d l o s s o f
c a rb o n d i o x i d e . T h i s m echanism h a s a l r e a d y b e e n d i s c u s s e d ,
t o some e x t e n t , i n S e c t i o n 2 . 1 . 2 . I t i s u n l i k e l y t h a t su ch
a mechanism i s o p e r a t i v e b e c a u s e t h e r a t e c o n s t a n t s a r e to o
83
h i g h f o r h y d ro g en a b s t r a c t i o n t o o c c u r , from th e s t r o n g 0 —̂ H
b ond o f th e c a rb o x y l g ro u p .
(b ) V ia I n i t i a l P r o to n T r a n s f e r
<2>p r o t o n A C — OH + RCCXg0 + RCOoHt r a n s f e r
e l e c t r o n
t r a n s f e r
A rg COH
The r a t e c o n s t a n t s , f o r e a c h o f t h e a c i d s , would be e x p e c te d
t o be o f t h e same o r d e r , i f t h i s mechanism were o p e r a t i n g .
A l s o , t h e e x c i t e d n , i r t r i p l e t s t a t e o f k e to n e s , w hich i s
in v o lv e d i n most o f t h e r e a c t i o n s , i s e l e c t r o p h i l i c i n
n a t u r e , t h u s r e n d e r i n g a c c e p ta n c e o f a p r o t o n an im p ro b a b le
p r o c e s s . Q uenching o f th e e x c i t e d s t a t e o f b i a c e t y l , by
p h e n o l , h a s b e en o b se rv e d ; how ever, t h e e v id e n c e p r e s e n t e d
do es n o t c o n c l u s i v e l y i n d i c a t e t h a t a p r o t o n t r a n s f e r i s
i n v o lv e d .
( c ) V ia E l e c t r o p h i l i c A t t a c k
XCHgCOgH
0
ArgCOH
- f < I > X C H 2
+ CO2
84
4%I t h a s b e e n p ro p o s e d t h a t t h e d e c a r b o x y l a t i o n o f c a r b o x y l i c
a c i d s , s e n s i t i s e d by b i a c e t y l , p r o c e e d s v i a su c h a mechanism
( s e e S e c t i o n 1 . 2 ) ; how ever, t h i s can o n ly be a p p l i e d t o
r e a c t i o n s o f a r y l - s u b s t i t u t e d a c i d s . I f t h i s mechanism were
o p e r a t i n g i n th e r e a c t i o n s s e n s i t i s e d by a r o m a t i c k e to n e s and
q u in o n e s , a d i f f e r e n t mechanism w ould have t o be p o s t u l a t e d
f o r d e c a r b o x y l a t i o n s o f a l i p h a t i c c a r b o x y l i c a c i d s . I t can
be s e e n from T ab le 1 3 , h o w ever , t h a t t h e r a t e c o n s t a n t s f o r
d e c a r b o x y l a t i o n o f (p h e n y l t h i o ) a c e t i c a c i d a n d S - ( n - b u t y l -
t h i o ) a c e t i c a c i d a r e o f th e same o r d e r . U n le s s t h i s i s
c o i n c i d e n t a l , i t i n d i c a t e s t h a t a s i m i l a r mechanism i s
o p e r a t i n g w i th t h e s e a c i d s . I n a d d i t i o n , such a mechanism
does n o t a c c o u n t f o r th e n o n - r e a c t i v i t y o f p h e n y l a c e t i c a c i d
to w a rd s a r o m a t i c k e to n e s and q u in o n e s .
E f f e c t o f O th e r A c id s on th e D e c a r b o x y la t io n s S e n s i t i s e d
by B enzophenone .
The e f f e c t o f a d d in g p h e n y l a c e t i c a c i d o r a c e t i c a c i d
to th e r e a c t i o n o f ( p h e n y l t h i o ) a c e t i c a c i d , s e n s i t i s e d by
b e n zo p h en o n e , i n benzene o r a c e t o n i t r i l e s o l u t i o n , was
i n v e s t i g a t e d . I r r a d i a t i o n p ro c e d u re C was u s e d ( s e e
e x p e r i m e n t a l s e c t i o n ) and th e r e s u l t s a r e shown i n T a b le 1 6 ,
[ I t m ust be n o te d t h a t n e i t h e r p h e n y l a c e t i c a c i d n o r a c e t i c
a c i d a r e d e c a r b o x y la te d u n d e r th e r e a c t i o n c o n d i t i o n s
u t i l i s e d ] .
85
•d(DCQ
♦H•P•HCQ
dS
•Hü
< <H"d
CM CMO 1 1
d 0 O O•iH > s 'd P P
*P P 'd *0 P < « 0 X 0ü d 1 0 00 0 *d m 0 in 0
P •rH CM ü CM üO O ü « • X
•H S < MD 0 MO 0
%g
•HP03
%0€COü
P
1gCQ'dpüC«HOpü
gM
vorH
(DI—ICOEh
gd
IoNd(DP
Xo•Hp
g«co
aS. ü
m o -d" -d"
< om
Td
I<
»d•rHü
g ^•rH dP P d S3co (D
s•rHEH
pd
>poco
mCM
üpp
8c
inCM
ü•rHP
8
mCM
ü•HP
8(A
rH
I
0 0 0 0d d d d0 0 0 0N N N Nd d d d0 0 0 0
m p p P
enMl ^
mCM
üpp
8CO
P
<D
S
pm
CMI
P<DO
S
LClr- iTv
CMI
p0o
s
0
g
s
O op p
X *X 0 X 0
0 0m 0 m 0CM ü CM 0
X • «MO 0 MO 0
ü 0•H •rHP P0 00 0
ü ü 0 0
g
s
0 0 0 0 0p 1—1 p P p•rH •rH •H •H pd d d d d
P p P P P0 •H •rH •tH P •Hd d d d d d0 o o o o oN p p p p pd 0 0 0 0 00 0 0 0 0 0
p < < < <
s$«
s
g•Hpüro8
S
OI—I
IP
m
$• d•Hü0
0
1HO
bOm
*
86
The r e s u l t s show t h a t , i n b e n ze n e s o l u t i o n , t h e added
a c i d s h a d a s l i g h t r e t a r d i n g e f f e c t on th e r a t e o f c a rb o n
d io x id e e v o l u t i o n , A m echanism i n v o lv i n g an i n i t i a l
p r o t o n t r a n s f e r c a n n o t be o p e r a t i n g , b e c a u se a d d i t i o n o f
e x c e s s a c e t i c o r p h e n y l a c e t i c a c i d would, be e x p e c te d t o quench
th e r e a c t i o n c o m p le te ly ( i . e . e q u a t i o n ( 2 ) d o m in a t in g o v e r
e q u a t i o n ( l ) , i n c o m p e t i t io n f o r th e e x c i t e d s t a t e o f th e
c a r b o n y l com pound)%
CH> / ,PhgC 0 + PhSCHg COg H -> PhgC-OH + PhSCHg COg ........ ( l )
PhgC— Ô + RCQsH -» PhgC— OH + RCO^ (2 )
R = CHg o r PhC%
A d d i t io n o f th e a c i d s t o r e a c t i o n s i n a c e t o n i t r i l e s o l u t i o n
c a u se d a marked i n c r e a s e i n th e y i e l d s o f c a rb o n d i o x id e .
I n a c e t o n i t r i l e s o l u t i o n , th e ( p h e n y l t h i o ) a c e t i c a c i d w i l l
be d i s s o c i a t e d , t o some e x t e n t , and a d d i t i o n o f o t h e r a c i d s
t o th e r e a c t i o n m ix tu re w i l l i n c r e a s e t h e ’ ’ c o n c e n t r a t i o n '*
o f u n d i s s o c i a t e d a c i d , i . e . t h e e q u i l i b r i u m ( 3 ) w i l l be
moved o v e r t o th e l e f t - h a n d s i d e I
jpSCHgCOgH # <|>SCH2CC^ + H (3 )
The p ro p o s e d mechanism f o r d e c a r b o x y l a t i o n , i n v o l v i n g
e l e c t r o n t r a n s f e r , r e q u i r e s th e p r e s e n c e o f t h e u n d i s s o c i a t e d
a c i d ; t h e r e f o r e , a d d i t i o n o f a c i d , t o r e a c t i o n s i n a c e t o n i t r i l e ,
s h o u ld enhance th e d e c a r b o x y l a t i o n r e a c t i o n , and t h i s i s
r e f l e c t e d in th e y i e l d s o f c a rb o n d i o x i d e , a s o b s e rv e d .
87
P h o sp h o re sc e n c e E m is s io n S tu d i e s
The e f f e c t o f ( p h e n y l t h i o ) a c e t i c a c i d on th e p h o sp h o r
e s c e n c e o f benzophenone i n m e th y lc y c lo h e x a h e g l a s s , a t 77°K,
was i n v e s t i g a t e d , w i th th e p o s s i b i l i t y t h a t e x c i p l e x e m is s io n
m ig h t be o b s e rv e d , from s p e c i e s su c h a s V I I I , The p h o s p h o r
e sc e n c e sp e c tru m o f a 2 x 10 ^ m o la r ’ s o l u t i o n ' o f benzophenone
i n m e th y lc y c lo h e x a n e , a t 77°K, was o b t a i n e d , u s i n g e x c i t a t i o n
a t 363 n m . ; e m is s io n maxima were o b s e rv e d a t 4 2 0 , 4 4 9 , 4 8 4 ,
and 520 nm,„ The sp e c tru m o f a s o l u t i o n o f ben zo phen one ,
c o n t a i n i n g ( p h e n y l t h i o ) a c e t i c a c i d , (2 x 10 ^ m o la r i n e a c h ) ,
i n m e th y lc y c lo h e x a n e g l a s s a t 77°K, was t h e n r u n , and t h e
e m is s io n o f benzophenone w as, t o a l l i n t e n t s and p u r p o s e s ,
u n c h an g ed . I t i s p o s s i b l e t h a t e x c i p l e x f o r m a t io n d o es n o t
o c c u r , u n d e r th e s e c o n d i t i o n s , due to p r e f e r e n t i a l f o r m a t io n
o f d im e rs o f th e a c i d , a s i n IX*
+. 1PhSCHg COH
PhgC - Cpv i n
tOPhSCHg C
•H-
-H-
0 .^ C — CHg SPh IX
88
9-“N i t r o a n t h r a c e n e Quenching: S t u d i e s ,
The d e c a r b o x y l a t i o n s s e n s i t i s e d by t e t r a c h i o r o - p - b e n z o -
qu in o n e w ere ta k e n a s b e in g r e p r e s e n t a t i v e o f th e d e c a rb o x y
l a t i o n r e a c t i o n s o f q u in o n e s i n g e n e r a l , f o r t h e p u r p o s e s o f
t h i s w ork . The r a t e c o n s t a n t s f o r t h e s e d e c a r b o x y l a t i o n s
c a n n o t be d e te r m in e d by n a p h th a le n e q u en ch in g s t u d i e s ,
(w h ich w ere u s e d f o r b e n z o p h e n o n e - s e n s i t i s e d r e a c t i o n s ) ,
b e c a u s e th e f i r s t e x c i t e d t r i p l e t s t a t e o f t e t r a c h l o r o - p -
b e n z o q u in o n e i s lo w e r i n e n e rg y th a n t h e f i r s t e x c i t e d t r i p l e t
s t a t e o f n a p h th a le n e . I t was fo u n d t h a t 9 - n i t r o a n t h r a c e n e
c o u ld a c t a s a s u i t a b l e q u e n c h e r i n t h a t i t d i d n o t fo rm a
com plex w i th th e q u in o n e , i t d i d n o t a c t a s an i n t e r n a l
f i l t e r , i t s f i r s t e x c i t e d t r i p l e t s t a t e was o f lo w e r e n e rg y
th a n th e q u in o n e , and i t d i d n o t b r i n g a b o u t th e d e c a rb o x y
l a t i o n o f th e a c i d s u n d e r th e c o n d i t i o n s u s e d .
The r a t e c o n s t a n t s , ( k ^ ) , f o r d e c a r b o x y l a t i o n o f
c a r b o x y l i c a c i d s , s e n s i t i s e d by t e t r a c h l o r o - p - b e n z o q u i n o n e ,
were d e te r m in e d , u s i n g 9 - u i t r o a n t h r a c e n e q u e n c h in g , from p l o t s
o f [BaCO g v e r s u s 9 - n i t r o a n t h r a c e n e c o n c e n t r a t i o n ,
[BaCOg
The r e s u l t s a r e shown i n T ab le 17 .
The r a t e c o n s t a n t f o r d e c a r b o x y l a t i o n o f N - ( o - c h l o r o -
p h e n y l ) g ly c in e c o u ld n o t be d e te rm in e d due to s o l u b i l i t y
d i f f i c u l t i e s .
89
T a b le 17 R a te C o n s t a n t s f o r th e T e t r a c h lo r o - p ~ b e n z o q u in o n e
- S e n s i t i s e d D e c a r b o x y la t io n o f C a rb o x y lI c i \ c i d s >
from 9 - N i t r o a n t h r a c e n e Quenching: S t u d i e s .
A d d S o lv e n t ( M ^ ^ .s e c " ^ . )o
P h e n o x y a c e t ic Benzene 6 .9 6 x 10
( P h e n y l t h i o ) a c e t i c Benzene 2 ,2 0 x 10^
I t c an be s e e n t h a t th e s e r a t e c o n s t a n t s a r e c o n s i d e r
a b ly g r e a t e r th a n th o s e o b t a i n e d from t h e c o r r e s p o n d in g
b e n z o p h e n o n e - s e n s i t i s e d r e a c t i o n s ( s e e T ab le 1 3 ) , a s e x p e c te d
from th e oxygen q u e n ch in g s t u d i e s . The f a c t t h a t th e r a t e
c o n s t a n t f o r d e c a r b o x y l a t i o n i s g r e a t e r f o r th e s u l p h u r a c i d
th a n f o r t h e oxy- a c i d i s e v id e n c e t h a t a mechanism i n v o lv i n g
an e l e c t r o n t r a n s f e r i n t h e r a t e - d e t e r m i n i n g s t e p i s
o p e r a t i n g i n th e q u i n o n e - s e n s i t i s e d d e c a r b o x y l a t i o n s , i n an
a n a lo g o u s manner t o th e b e n z o p h e n o n e - s e n s i t i s e d d e c a r b o x y la
t i o n s . T e t r a c h lo r o - p - b e n z o q u in o n e i s known t o form
com plexes w i th compounds c o n t a i n i n g h e t e r o a tom s e . g .91am ines , an d , a s a r e s u l t i t i s p r o b a b le t h a t t h e r a t e -
d e te r m in in g e l e c t r o n t r a n s f e r s t e p becomes more e f f i c i e n t
t h a n i n th e c ase o f th e benzophenone r e a c t i o n s , a s r e f l e c t e d
i n th e r a t e c o n s t a n t s f o r d e c a r b o x y l a t i o n o b t a i n e d .
90
2 .2 Expe Pimentai
2 . 2 . 1 I n s t r u m e n t a t i o n
'H n u c l e a r m a g n e tic r e s o n a n c e s p e c t r a were r e c o r d e d f o r
s o l u t i o n s i n d e u te r io c h l o r o f o r m (w i th t e t r a m e t h y l s i l a n e a s
i n t e r n a l s t a n d a r d ) , u n l e s s o th e r w is e s t a t e d , w i th a V a r ia n
T60 s p e c t r o m e t e r .
I n f r a r e d s p e c t r a , f o r sam p les i n N u jo l m u l l , were
r e c o r d e d on a P e r k i n E lm er 237 o r 257 s p e c t r o p h o to m e te r .
D e te r m in a t io n s o f c a rb o n y l a b s o r p t i o n , by i n f r a r e d s p e c t r o
sc o p y , were c a r r i e d o u t , f o r s o l u t i o n s i n b e n z e n e , u s i n g a
Unicam SP 200 s p e c t r o p h o to m e te r .
U l t r a v i o l e t s p e c t r a were r e c o r d e d on a Unicam SP 800
s p e c t r o p h o to m e te r . D e te r m in a t io n s o f b en zo p h en o n e , by u l t r a
v i o l e t s p e c t r o s c o p y were c a r r i e d o u t u s i n g a H i l g e r a n d W a tts
H 11 3 5 .1 s p e c t r o p h o to m e te r .
Mass s p e c t r a were ru n on an A . E . I . MS9 mass s p e c t ro m e te r ,
I n eac h c a se th e m o le c u la r io n i s g iv e n f i r s t , f o l lo w e d by
p e ak s o f s t r u c t u r a l s i g n i f i c a n c e .
M e l t i n g p o i n t s were d e te rm in e d on a K o f l e r B lo c k , u s i n g
c o r r e c t e d th e rm o m e te r s .
91
E le m e n ta l A n a ly s e s were c a r r i e d o u t by R a p id E le m e n ta l
A n a ly s e s , B e a c o n s f i e l d ,
P h o s p h o re s c e n c e s p e c t r a were r e c o r d e d w i th a B a i r d
A tom ic F l u o r i s p e c , model SP lOOE.
2 . 2 . 2 A n a ly s e s by Gas L iq u id C hrom atography
A n a ly s e s w ere c a r r i e d o u t w i th a P e r k i n E lm er F l l gas
c h ro m a to g ra p h , e q u ip p e d w i th a f lam e i o n i s a t i o n d e t e c t o r .
The d e t e c t o r gave a l i n e a r r e s p o n s e o v e r t h e w hole r a n g e o f
c o n c e n t r a t i o n s u s e d . P r o d u c t s were c o n f i rm e d by a co m p ar iso n
o f t h e i r r e t e n t i o n t im e s w i th th o s e o f a u t h e n t i c m a t e r i a l s .
Q u a n t i t a t i v e e s t i m a t i o n o f th e p r o d u c t s was c a r r i e d o u t by
com paring t h e a r e a o f th e e l u t i o n p e a k , f o r t h e p r o d u c t ,
w i th t h a t f o r a n a u t h e n t i c sa m p le , from a s o l u t i o n o f known
c o n c e n t r a t i o n . More th a n one d e t e r m i n a t i o n was a lw a y s made.
I n a l l c a s e s th e p eak a r e a s were r e p r o d u c i b l e t o w i t h i n 5%.
The a m in es were d e te rm in e d u s i n g a column p a c k e d w i th
18% Carbowax 1500 on Chrom osorb W s u p p o r t , a t 1 5 0 ° . A n i s o l e
a n d m e th y l p h e n y l s u lp h id e were d e te rm in e d on a column p a c k e d
w i th 10% A p ie z o n L on Chromosorb P , a t 120° and 140° ,
r e s p e c t i v e l y . F o r r e a c t i o n s i n v o l v i n g benzophenone and
q u in o n e s , n - b u t y l m eth y l s u lp h id e was d e te r m in e d on a column
p a c k e d w i th 28% P e n w a l t + 4% p o ta s s iu m h y d ro x id e on 80-100
mesh Gas-Chrom R ( s u p p l i e d by A p p l i e d S c ie n c e L a b s . I n c . ) ,
a t 1 8 0 ° . F o r r e a c t i o n s i n v o lv i n g t h e o t h e r a r o m a t i c k e t o n e s .
92
n - b u t y l m e th y l s u lp h id e was d e te r m in e d on a column p a c k e d w i th
15% A p ie z o n L on Chrom osorb P , a t 1 0 0 ° . I n a l l c a s e s , t h e
d im e n s io n s o f t h e colum ns u s e d were 7 .5 f t . x 0 . 125i n . .
R e ag e n ts and S t a r t i n g M a t e r i a l s
N i t r o g e n ( o x y g e n - f r e e ) a n d oxygen were f r e e d from c a rb o n
d io x id e by p a s s a g e th ro u g h a s a t u r a t e d b a r iu m h y d ro x id e
s o l u t i o n . The 'c a r b o n d i o x i d e - f r e e * g a s e s were d r i e d by
p a s s a g e th ro u g h c o n c e n t r a t e d s u l p h u r i c a c i d a n d o v e r sodium
h y d ro x id e p e l l e t s . Benzene was h e a t e d , u n d e r r e f l u x , w i th
c a lc iu m h y d r i d e , and d i s t i l l e d , u n d e r n i t r o g e n o r oxygen , a s
r e q u i r e d . A c e t o n i t r i l e was d i s t i l l e d u n d e r n i t r o g e n . The
l i g h t p e t r o le u m u s e d f o r ch ro m a to g rap h y h a d b . p . 40- 60° ,
u n l e s s o th e r w is e s t a t e d . The b a s i c a lu m in a u s e d i n chrom a
to g ra p h y was L a p o r t e Type *H* and th e s i l i c a was M.P.C.
s i l i c a .
The f o l lo w in g m a t e r i a l s were r e c r y s t a l l i s e d ; t e t r a c h l o r o -
p -b e n z o q u in o n e , m .p . 290° (from e t h a n o l ) ; 9 , 10- p h e n a n t h r a -
q u in o n e , m .p . 208° (from e t h a n o l ) ; 9 , 10- a n t h r a q u in o n e , m .p .
286° (from b e n z e n e ) ; x a n th o n e , m .p. 174° (from e t h a n o l ) ;
f l u o r e n o n e , m .p . 83° (from e t h a n o l ) ; 2- a c e t y l n a p h t h a l e n e ,
m .p . 56° (from e t h a n o l - w a t e r , 5 0 :5 0 v / v ) ; p - b e n z o q u in o n e ,
m .p . 116° (from e t h a n o l - w a t e r , 5 0 :50 v / v ) . A c e to p h e n o n e ,
b . p . 65° a t 5 mm. Hg, was d i s t i l l e d u n d e r n i t r o g e n . A l l
o t h e r compounds were u s e d w i th o u t f u r t h e r p u r i f i c a t i o n and
w ere s u p p l i e d by B .D .H . o r K o c h -L ig h t C h em ica ls L t d . .
93
2 . 2 . 3 P r e p a r a t i o n o f M a t e r i a l s
P r e p a r a t i o n o f N - ( o - c h l o r o p h e n y l )g ly c in e
o - C h l o r o .a n i l i n e (1 2 .5 g . , 0 .1 m o le s ) , 96% e t h a n o l (20 g . ) ,
30% p o ta s s iu m h y d ro x id e s o l u t i o n ( 2 .5 g . ) , and 40% form
a ld e h y d e s o l u t i o n (4 g . ) , were h e a t e d t o b o i l i n g , w i th
s t i r r i n g . A 49% p o ta s s iu m c y a n id e s o l u t i o n (7 g . ) was v e ry
c a r e f u l l y a d d ed , an d th e m ix tu re r e f l u x e d f o r 3 h o u r s a t
8 1 - 2 ° . A f t e r s team d i s t i l l i n g o f f t h e a l c o h o l and e x c e s s
o - c h l o r o a n i l i n e , t h e N - ( o - c h i o r o p h e n y l ) g l y c i n e was p r e c i p i t a t e d
by a d d in g d i l u t e s u l p h u r i c a c i d . R e c r y s t a l l i s a t i o n from
w a t e r - e t h a n o l (9 .t l v / v ) gave w h i te n e e d l e s o f IT -(o -c h i o r o
p h e n y l )g l y c i n e .
Y i e ld : 4 . 8 g . (73% th e o r y )
m .p . 1 70 -1 “ ( L i t f 'm . p . 171“ )
P r e p a r a t i o n o f S - ( n - b u t . y l t h i o ) a c e t i c a c i d
A c o n c e n t r a t e d , a q u eo u s s o l u t i o n o f c h l o r o a c e t i c a c i d
(9 .3 g . , 0 .1 m o l e s ) , p r e v i o u s l y n e u t r a l i s e d w i th sodium
c a r b o n a t e , was p o u re d i n t o a m ix tu re o f n - b u t y l m e rc a p ta n
(9 .0 g . , 0 .1 m o les) and sodium h y d ro x id e (4 .0 g , ) , i n 20 m l.
w a t e r . The m ix tu re was r e f l u x e d f o r one h o u r and th e n s te am
d i s t i l l e d , u n t i l o n ly one l a y e r r e m a in e d . The s o l u t i o n was
f i l t e r e d a n d S - ( n - b u t y l t h i o ) a c e t i c a c i d s e p a r a t e d , on a d d i t i o n
o f d i l u t e s u l p h u r i c a c i d . T h is was s e p a r a t e d o f f , d r i e d
o v e r a n h y d ro u s magnesium s u l p h a t e , and d i s t i l l e d u n d e r vacuum.
94
g i v in g S - ( n - b u t y l t h i o ) a c e t i c a c i d a s a c o l o u r l e s s l i q u i d .
Y ie ld : 3 . 7 g . (40% t h e o r y )
b . p . 121° a t 2mm. Hg93
( L i t . b . p . 140-4° a t 1 0 -1 5 mm. Hg)
P r e p a r a t i o n o f ( p h e n y l t h i o ) a c e t i c a c i d
P h en y l m e rc a p ta n ( l l g . , 0 .1 m o le ) , c h lo ro a c e t ic a c i d
(9 .5 g . , 0 .1 m o le ) , sodium h y d ro x id e (10 g . ) , and 250 ml.
w a te r were h e a t e d on a s team b a t h f o r f i f t e e n m in u te s .
The m ix tu re was c o o le d and a c i d i f i e d w i th c o n c e n t r a t e d
h y d r o c h l o r i c a c i d . A y e l lo w o i l s e p a r a t e d o u t , w hich
s o l i d i f i e d on s t a n d i n g . R e c r y s t a l l i s a t i o n from b e n z e n e -
p e t ro le u m e t h e r , b . p . 60- 80° , ( 1%10 v / v ) , gave w h i te c r y s t a l s
o f ( p h e n y l t h i o ) a c e t i c a c i d .
Y ie ld : 6 .0 g . (40% th e o r y )
m .p . 6 1 -6 2 .5 ° ( L i t ^ m . p . 6 3 - 6 3 .5 ° )
95P r e p a r a t i o n o f 3 . 5 -d im e th o x y p h e n o x y a c e t ic a c i d
A 50% aq ueou s s o l u t i o n o f c h lo ro a c e t ic a c i d (10 m l . )
was added t o a m ix tu re o f 3 , 5-d im e th o x y p h e n o l (4 .5 g . , 0 .0 3
m o le s ) and 33% sodium h y d ro x id e s o l u t i o n (10 m l . ) . A f t e r
c o o l i n g , th e m ix tu re was d i l u t e d w i th w a te r (20 m l . ) , made
a c i d ( t o Congo Red) w i th d i l u t e h y d r o c h l o r i c a c i d , and
e x t r a c t e d w i th d i e t h y l e t h e r (50 m l . ) . The e t h e r e a l e x t r a c t
was washed w i th w a te r (20 m l . ) , and extiBCbed w i th 5% sodium
95
c a r b o n a t e s o l u t i o n (50 m l . ) . The sodium c a r b o n a te e x t r a c t
was a c i d i f i e d ( t o Congo Red) w i th d i l u t e h y d r o c h l o r i c a c i d ,
and t h e 3 , 5- d im e th o x y p h e n o x y a c e t ic a c i d , w hich s e p a r a t e d w i th
c o n s i d e r a b l e d i f f i c u l t y , was r e c r y s t a l l i s e d from h o t w a te r .
Y ie ld I 0 .9 g . (15% t h e o r y )
m .p . 120- 2*
P r e p a r a t i o n o f N - m e t h y l - o - c h l o r o a n i l i n e
The f o l l o w i n g r e a c t i o n se q u en c e was u t i l i s e d !
^ + HCOgH ^ ^ HNHCHO ^ ^ NHCHj
96P r e p a r a t i o n o f o - c h l o r o f o r m a n i l i d e l o - C h l o r o a n i l i n e
(25 g . , 0 .2 m o le s ) , 85% fo rm ic a c i d s o l u t i o n (20 g . ) , and
t o lu e n e (200 m l . ) were p l a c e d i n a 500 m l. ro u n d -b o t to m e d
f l a s k , f i t t e d w i t h a w a te r c o n d e n s e r s e t f o r downward
d i s t i l l a t i o n . The m ix tu re was d i s t i l l e d s lo w ly , u n t i l a l l
t h e w a te r h a d b e e n rem oved, a s th e a z e o t r o p e w i th to lu e n e ;
t h e t e m p e r a tu r e t h e n r o s e t o 1 0 8 -1 1 0 * . The m a j o r i t y o f th e
t o lu e n e was rem oved by d i s t i l l a t i o n , and th e r e s i d u e r e c r y s t
a l l i s e d from p e t r o le u m e t h e r , b . p . 60- 80* , t o g iv e w h i te
c r y s t a l s o f o - c h l o r o f o r m a n i l i d e .
96
Y i e ld ! 25g . (80% t h e o r y )
m .p . 76-7° ( L i t ? m .p . 77° )
R e d u c t io n o f o - c h l o r o f o r m a n i l i d e I L i th iu m a lum in ium h y d r id e
(4 g . ) a n d d i e t h y l e t h e r (100 m l . ) were p l a c e d i n a 500 m l,
t h r e e - n e c k e d f l a s k , f i t t e d w i th a r e f l u x c o n d e n s e r , m e c h a n ic a l
s t i r r e r , and a d ro p p in g f u n n e l c o n t a i n i n g o - c h l o r o f o r m a n i l i d e
( 2 5 g . , 0 .1 5 m o le s ) i n d i e t h y l e t h e r (100 m l . ) . The
o - c h l o r o f o r m a n i l i d e s o l u t i o n was ad d ed d ro p w is e , w i t h
v ig o r o u s s t i r r i n g . A f t e r th e a d d i t i o n , th e s o l u t i o n was
s t i r r e d f o r one h o u r . The p r o d u c t s o l u t i o n was f i l t e r e d
th ro u g h a s i n t e r , and th e f i l t r a t e d r i e d o v e r a n h y d ro u s
magnesium s u l p h a t e . The e t h e r was t h e n rem oved on a w a te r
b a t h , and th e r e s i d u e d i s t i l l e d u n d e r vacuum. N -m e th y l -o -
c h l o r o a n i l i n e was d i s t i l l e d a s a c o l o u r l e s s l i q u i d , w hich
r a p i d l y t u r n e d brown on e x p o su re t o a i r .
Y i e ld : 7 .0 g . (30% t h e o r y )
b . p . 50° a t 0 . 7 mm.Hg.
( L i t ? b . p . 215-6° a t 760 mm. Hg)
2 .2 .U D e te r m in a t io n o f C arbon D io x id e
S e v e r a l m ethods o f d e te r m in in g c a rb o n d i o x i d e , p ro d u c e d
i n th e r e a c t i o n s i n v e s t i g a t e d , were a t t e m p t e d . I t i s
i n s t r u c t i v e t o c o n s i d e r th e p r o s a n d co n s o f t h e p h y s i c a l
t e c h n iq u e s w hich can be em ployed , a n d th u s a s h o r t su rv e y
i s g iv e n h e re !
97
( i ) V o lu m e tr ic M e th o d s . I n t h e o r y t h i s w ould p r o v id e a
c o n v e n ie n t and d i r e c t - r e a d i n g way o f d e te r m in in g th e c a rb o n
d io x id e e v o lv e d ; h o w ev er , th e s o l u b i l i t y o f c a rb o n d io x id e98
i n b e n z e n e , a t 25° C, i s 2 .4 c c , p e r c c . o f b en ze n e ( c . f .
s o l u b i l i t y o f n i t r o g e n i n b e n z e n e , a t 25°C, i s 0 .1 2 c c . p e r 99 \
C C . o f ben zen e ) . H ence , th e c a rb o n d io x id e w i l l re m a in
i n s o l u t i o n , t o some e x t e n t , and i n c o r r e c t r e s u l t s o b t a i n e d .
I n an a t t e m p t t o overcome t h i s p ro b le m , b e n z e n e , s a t u r a t e d
w i th c a rb o n d i o x id e , was u t i l i s e d a s t h e s o l v e n t ; how ever,
co m parison o f th e y i e l d s o f c a rb o n d io x id e o b t a i n e d , w i th
th o s e o b t a i n e d by o t h e r m etho ds , e . g . g r a v i m e t r i c a l l y v i a
b a riu m c a r b o n a te ( s e e l a t e r ) , showed t h a t t h e v o l u m e t r i c
m ethod was s t i l l g i v in g enorm ous e r r o r s .
( i i ) V ia S p e c t r o s c o p ic and C h ro m a to g ra p h ic Methods The
s p e c t r o s c o p i c m ethods a l l f o l lo w t h e d e c r e a s e i n a c i d
c o n c e n t r a t i o n , r a t h e r t h a n c a rb o n d io x id e e v o l u t i o n .
U l t r a v i o l e t s p e c t r o s c o p y c a n n o t be u s e d b e c a u s e , i n many c a s e s ,
th e c a rb o n y l compound, w hich i s t h e s e n s i t i s e r f o r th e
r e a c t i o n , a b s o r b s i n t h e same r e g i o n a s t h e a c i d ; a l s o , t h e r e
i s th e p o s s i b i l i t y t h a t i n t e r m e d i a t e s may g iv e a n a b s o r p t i o n .
I n f r a r e d s p e c t r o s c o p y a n d n u c l e a r m a g n e t ic r e s o n a n c e
s p e c t r o s c o p y a r e l i m i t e d i n t h e i r u s a g e , a s b o th r e q u i r e __2
s o l u t i o n s o f 10" m o la r c o n c e n t r a t i o n , o r g r e a t e r ; f o r
exam p le , th e y c o u ld n o t be u s e d t o f o l lo w r e a c t i o n s o f
N - ( o - c h io r o p h e n y 1 ) g l y c i n e i n b e n ze n e s o l u t i o n , b e c a u s e th e
a c i d i s o n ly s p a r i n g l y s o l u b l e i n t h i s s o l v e n t .
98
Gas l i q u i d c h ro m a to g rap h y c o u ld be u s e d t o f o l lo w
f o rm a t io n o f c a rb o n d i o x id e ; ho w ev er , t h i s t e c h n iq u e h a s
f a i r l y h i g h i n h e r e n t e r r o r s , p a r t i c u l a r l y when w o rk in g a t
low c o n c e n t r a t i o n s .
( i i i ) V ia G r a v im e t r i c M ethods  g r a v i m e t r i c m ethod ,
f o r d e t e r m i n a t i o n o f c a rb o n d i o x id e , was u t i l i s e d i n t h e work
p r e s e n t e d i n t h i s t h e s i s . The c a rb o n d i o x i d e , e v o lv e d i n
th e r e a c t i o n s , was p r e c i p i t a t e d a s b a r iu m c a r b o n a te by
p a s sa g e th ro u g h a s a t u r a t e d b a r iu m h y d ro x id e s o l u t i o n . The
c a r b o n a te , a f t e r f i l t r a t i o n th ro u g h a s i n t e r e d g l a s s c r u c i b l e ,
was d r i e d t o c o n s t a n t w e ig h t , t h u s a f f o r d i n g t h e y i e l d o f
c a rb o n d i o x i d e . Y ie ld s were r e p r o d u c i b l e t o w i t h i n + 2%,
(T h is m ethod was p r e f e r r e d t o one i n v o l v i n g ’b a c k - t i t r a t i o n *
o f th e b a r y t a s o l u t i o n ) .
2 . 2 . 5 I r r a d i a t i o n P r o c e d u re s
I r r a d i a t i o n P ro c e d u re A I F o r t h e D e te r m in a t io n o f t h e
R e l a t i v e Y ie ld s o f C arbon D io x id e .
An im m ersion a p p a r a t u s was u s e d , i n w hich a 100 w a t t
H anovia medium p r e s s u r e m ercury lamp was c o n ta in e d i n a
P y re x w a t e r - c o o l e d w e l l . The r e a c t i o n m ix tu re ( i n b e n ze n e
[160 m l . ] ) s u r ro u n d e d t h i s w e l l an d was s t i r r e d by means o f
a s t r e a m o f n i t r o g e n , w hich was a d m i t t e d th ro u g h a s i n t e r .
The e x i t g a s e s were p a s s e d th ro u g h two wash b o t t l e s i n s e r i e s ,
c o n ta in i n g s a t u r a t e d b a r iu m h y d ro x id e s o l u t i o n . I n e a c h-3c a se th e r e a c t i o n m ix tu r e s were 3 .1 3 x 10 M i n a c i d a n d
99
c a r b o n y l compound. The r e a c t i o n m ix tu re was p u rg e d th r o u g h
o u t t h e i r r a d i a t i o n , f o r t h r e e h o u r s , a n d a l s o f o r a n h o u r ,
b e f o r e an d a f t e r i r r a d i a t i o n . The y i e l d o f c a rb o n d io x id e
was d e te rm in e d a s a b o v e .
I r r a d i a t i o n P ro c e d u re B % F o r D e te r m in a t io n o f t h e Y ie ld s
o f S u b s t i t u t e d H y d ro c a rb o n s .
 B ay o n e t P h o to c h e m ic a l R e a c to r , e q u ip p e d w i th lam ps
h a v in g maximum e m is s io n a t 350 nm, was em ployed . I n a l l
c a s e s th e r e a c t i o n m ix tu r e s were 6 .2 5 x 10” M i n th e a c i d and
t h e c a r b o n y l compound. The r e a c t i o n m ix tu re ( i n b e n ze n e
[10 m l , ] ) was c o n ta in e d i n a P y re x tu b e an d was c o n t i n u o u s l y
p u rg e d w i th n i t r o g e n , t h e e x i t g a s e s b e in g p a s s e d th r o u g h two
wash b o t t l e s i n s e r i e s c o n t a i n i n g s a t u r a t e d b a r y t a s o l u t i o n ;
t h e c a rb o n d io x id e was d e te rm in e d a s a b o v e . S o l u t i o n s were
p u r g e d w i th n i t r o g e n f o r one h o u r , b e f o r e and a f t e r i r r a d i a t
i o n . The y i e l d s o f s u b s t i t u t e d h y d ro c a rb o n s were d e te rm in e d
by g a s - l i q u i d ch ro m a to g ra p h y .
I r r a d i a t i o n P ro c e d u re C I F o r D e te r m in a t io n o f th e Y i e ld s
o f C arbon D io x id e from M e c h a n i s t i c S t u d i e s .
The r e a c t i o n m ix t u r e s , which were 6 .2 5 x 10 i n t h e
a c i d and c a rb o n y l compound, ( i n b enzen e o r a c e t o n i t r i l e
[12 m l . ] ) were p u rg e d w i th n i t r o g e n f o r one h o u r , a f t e r
w hich t im e th e volume o f s o l u t i o n was r e d u c e d to 10 m l . , The
P y re x t u b e s , c o n t a i n i n g th e r e a c t i o n m ix t u r e s , were p l a c e d
100
i n a 'm e r ry -g o - ro u n d * a p p a r a t u s c o n ta in e d i n a R ayo net
P h o to c h e m ic a l R e a c to r , e q u ip p e d w i th lam ps h a v in g maximum
e m is s io n a t 350 nra ( f o r r e a c t i o n s i n v o lv i n g b en zo phen one) o r
313 nm ( f o r r e a c t i o n s i n v o lv i n g t e t r a c h l o r o - p - b e n z o q u i n o n e ) .
A f t e r i r r a d i a t i o n , th e s o l u t i o n s were p u rg e d w i th n i t r o g e n
f o r one h o u r , t h e e x i t g a s e s b e in g p a s s e d th ro u g h s a t u r a t e d
b a r y t a s o l u t i o n s ; th e y i e l d o f c a rb o n d io x id e was d e te r m in e d
a s ab o v e , [ i t m ust be n o te d t h a t th e r e a c t i o n m ix tu r e s
were n o t p u rg e d w i th n i t r o g e n d u r in g i r r a d i a t i o n ] ,
2 . 2 . 6 B lank P h o to ly s e s o f t h e A c id s
I r r a d i a t i o n o f N - ( o -c h io ro p h e n y 1 ) g l y c i n e , S - ( n - b u t y l t h i o ) -
a c e t i c a c i d , ( p h e n y l t h i o ) a c e t i c a c i d , p h e n o x y a c e t ic a c i d ,
a c e t i c a c i d , o r p h e n y l a c e t i c a c i d , i n b e n ze n e o r a c e t o n i t r i l e
s o l u t i o n (3 .1 3 X 10 o r 6 .2 5 x 10” ^M), u s i n g th e 100 w a t t
H anovia medium p r e s s u r e m ercu ry lamp o r th e R ay o n e t R e a c to r
(350 nm. l a m p s ) , gave n e g l i g i b l e y i e l d s o f c a rb o n d i o x i d e , i n
a l l c a s e s .
2 . 2 . 7 P r o d u c t S t u d i e s
I r r a d i a t i o n o f B enzene S o l u t i o n o f Benzophenone C o n ta in in g
P h e n o x y a c e t ic A c id
A benzen e s o l u t i o n (150 m l . . ) o f benzophenone (1 .8 2 g . )
c o n ta in i n g p h e n o x y a c e t ic a c i d ( 1 .5 2 g . ) was i r r a d i a t e d u n d e r
n i t r o g e n i n th e H anovia r e a c t o r f o r s i x h o u r s , a f t e r w hich
tim e c a rb o n d io x id e e v o l u t i o n was v e ry s low . The s o l u t i o n
was e v a p o r a te d to g iv e a sem i—c r y s t a l l i n e mass w hich was
101
t r i t u r a t e d w i th l i g h t p e t r o le u m . The i n s o l u b l e c r y s t a l l i n e
m a t e r i a l was r e c r y s t a l l i s e d from b e n z e n e - l i g h t p e t ro le u m
(50 I 50 v / v ) t o g iv e 1 , 1 ’ , 2 , 2 * - t e t r a p h e n y l e t h y l e n e g ly c o l
(1 g . ) , m .p . and m ixed m .p . 1 8 5 -6 ° . The o i l y m o th e r l i q u o r
m a t e r i a l ( o .9 g . ) was d i s s o l v e d i n b e n ze n e and e x t r a c t e d
w i th 2N-sodium h y d ro x id e s o l u t i o n , t o g iv e un ch an ged
p h e n o x y a c e t ic a c i d ( 0 .2 g . ) .
The benzene s o l u t i o n was e v a p o r a t e d t o g iv e a y e l lo w
o i l (0 .7 g . ) w hich was c h ro m a to g ra p h ed on a lu m in a (15 g . ) .
E l u t i o n w i th l i g h t p e t r o l e u m - e t h e r (20 ! 1 t o 10 ! 1 v / v )
gave benzophenone ( 0 .3 g . ) , which was i d e n t i f i e d by i . r .
s p e c t r o s c o p y . The l i g h t p e t r o le u m f r a c t i o n ( 1 .2 5 g . ) ,
from th e t r i t u r a t i o n , wr-s c h ro m a to g ra p h ed on a lu m in a (30 g . ) .
E l u t i o n w i th l i g h t p e t r o le u m gave 1 , 2 - d ip h e n o x y e th a n e ( 0 .1 g , )
m .p , 9 7 - 8 ° , ( l i t . * ^ m .p . 9 8 ° ) , ( i . r . and n . m . r . i d e n t i c a l
w i th t h a t o f an a u t h e n t i c compound).
Gas l i q u i d ch ro m a to g rap h y s t u d i e s showed t h a t a m ajo r
p r o d u c t o f th e r e a c t i o n , a n i s o l e , was l o s t on e v a p o r a t i o n
o f th e s o l v e n t b e n z e n e . The y i e l d o f t h i s p r o d u c t was
d e te rm in e d by g . l . c . o f th e s o l u t i o n d i r e c t l y a f t e r i r r a d i a t
io n ( s e e T a b le 3 ) .
I r r a d i a t i o n o f a Benzene S o l u t i o n o f Benzophenone c o n t a i n i n g
(P h e n y l t h i o ) a c e t i c A c id
A b en zene s o l u t i o n ( 16O m l . ) o f benzophenone (1 .8 2 g . )
c o n t a i n i n g ( p h e n y l t h i o ) a c e t i c a c i d (1 .6 8 g . ) was i r r a d i a t e d
102
u n d e r n i t r o g e n f o r t h r e e h o u r s , w i th th e H anovia r e a c t o r .
The s o l u t i o n was e v a p o r a t e d t o g iv e a semi - c r y s t a l l i n e mass
( 2 .9 g . ) which was t r i t u r a t e d w i th l i g h t p e t r o l e u m . The
i n s o l u b l e m a t e r i a l ( 1 .3 g . ) gave 1 , 1 ’ , 2 , 2 ’ - t e t r a p h e n y l e t h y l e n e
g l y c o l ( 0 .7 g . ) , m .p . a n d m ixed m .p . 1 8 5 - 6 ° , from b e n z e n e -
l i g h t p e t r o le u m (1 t 5 v / v ) . The m o th e r l i q u o r s were
c h ro m a to g ra p h ed on a lu m in a (20 g . ) . E l u t i o n w i th l i g h t
p e t r o l e u m - e t h e r ( l 6 % 1 v / v ) gave benzophenone ( 0 ,1 5 g . )
( i d e n t i f i e d by i . r . s p e c t r o s c o p y ) . The l i g h t p e t r o le u m
f r a c t i o n ( 1 .6 g . ) , from th e t r i t u r a t i o n , was shown by g . l . c .
t o c o n t a i n m e th y l p h e n y l s u lp h id e (0 .6 2 g . ) . A l s o , by
means o f q u a n t i t a t i v e i . r . s p e c t r o s c o p y , t h i s f r a c t i o n was
shown t o c o n t a i n benzophenone ( 0 .5 g . )•
I r r a d i a t i o n o f a Benzene S o l u t i o n o f Benzophenone c o n t a i n i n g
N - (o -C h lo ro p h e n v l ) g l y c i n e .
A b en zen e s o l u t i o n (750 m l . ) c o n t a i n i n g benzophenone
( 1 .8 2 g . ) and N - ( o - c h io r o p h e n y l ) g ly c in e ( 1 .8 6 g . ) was
i r r a d i a t e d f o r e i g h t h o u r s w i th t h e H anov ia r e a c t o r . The
s o l u t i o n was e v a p o r a t e d a n d t h e r e s i d u e was c h ro m a to g ra p h ed
on s i l i c a (60 g . ) . E l u t i o n w i th l i g h t p e t ro le u m -b e n z e n e
(3 I 1 v / v ) gave benzophenone ( 0 .5 g . ) , w h ich was i d e n t i f i e d
by i . r . s p e c t r o s c o p y . E l u t i o n w i th l i g h t p e t r o l e u m - e t h e r
(1%1 v / v ) gave 1 , 1 * , 2 , 2 * - t e t r a p h e n y l e t h y l e n e g l y c o l ( 0 .7 5 g . ) ,
m .p . and m ixed m .p . 1 8 5 - 6 ° . The am ines p ro d u c e d i n t h e
r e a c t i o n rem a in e d a b s o rb e d t o th e colum n; t h e i r y i e l d s were
d e te rm in e d by g . l . c . on th e r e a c t i o n m ix tu re ( s e e T a b le 6 ) .
103
I r r a d i a t i o n o f a Benzene S o l u t i o n o f T e t r a c h l o r o - p - b e n z o
qu inone c o n ta in in g : P h e n o x y a c e t ic A c id
A ben zen e s o l u t i o n (160 m l . ) o f t e t r a c h l o r o - p - b e n z o -
qu inone (0 .4 9 g , ) c o n t a i n i n g p h e n o x y a c e t ic a c i d (0 .3 0 g . )
was i r r a d i a t e d f o r tw e lv e h o u r s , w i th th e H anov ia r e a c t o r ,
t o g iv e a 93% y i e l d o f c a rb o n d i o x i d e . The s o l u t i o n was
e v a p o r a t e d and th e r e s i d u e c h ro m a to g ra p h ed on s i l i c a ( 4 2 g . ) .
E l u t i o n w i th l i g h t p e t r o l e u m - e t h e r (30 I 1 v / v ) gave
t e t r a c h l o r o - p - b e n z o q u i n o n e ( 0 .0 4 g . ) , which was i d e n t i f i e d
by i . r . s p e c t r o s c o p y . E l u t i o n w i th l i g h t p e t r o l e u m - e t h e r
(33 I 1 v / v ) gave a c r y s t a l l i n e s o l i d ( 0 .3 8 g . ) . R e c r y s t a l l
i s a t i o n from l i g h t p e t r o le u m ( b . p . 60-80° ) gave 0 - ( p h e n o x y -
m e t h y l ) - 2 , 3 , 5 , 6 - t e t r a c h l o r o q u i n o l (0 ,3 2 g . ) .
Y ie ld : 0 .3 2 g . (30% t h e o r y )
m .p . 137-8°
i . r . ̂ 3 , 3 8 0 , 9 6 5 , and 750-690 cm” ^
n . m . r , 2 . 6T (5 h y d ro g e n m u l t i p l e t )
4 . 1 X (2 h y d ro g en s i n g l e t )
A n a l y s i s : Pound: C, 4 4 .0 1 ; H, 2 .9 0 ; C l , 40.31%
CioHgCl^Os r e q u i r e s C, 4 4 .1 5 ; H ,2 .7 0 ; 0 1 , 40.15%
Mass sp e c tru m : m/e 352 (0 1 = 3 5 ) , M^-107, 225 (01=35)
I r r a d i a t i o n o f a Benzene S o l u t i o n o f T e t r a c h l o r o - p - b e n z o
quinone c o n t a i n i n g ( P h e n y l t h i o ) a c e t i c A c id
A b en zen e s o l u t i o n ( l6 0 m l . ) o f t e t r a c h l o r o - p - b e n z o
qu in one ( 0 .3 7 g . ) c o n t a i n i n g ( p h e n y l t h i o ) a c e t i c a c i d ( 0 .2 5 g . )
104
was i r r a d i a t e d f o r 4 . 5 h o u r s , w i th th e H anovia r e a c t o r , t o
g iv e a 95% y i e l d o f c a rb o n d i o x i d e . The s o l u t i o n was
e v a p o r a t e d and th e r e s i d u e was c h ro m a to g ra p h e d on s i l i c a
(20 g . ) , E l u t i o n w i th l i g h t p e t r o l e u m - e t h e r (50 % 1 v / v )
gave a m ix tu re o f t e t r a c h l o r o - p - b e n z o q u i n o n e ( 0 .0 3 g . ) and
t h io p h e n o l . An a u t h e n t i c m ix tu re o f t h e s e two compounds
had an i . r . sp e c tru m i d e n t i c a l t o t h a t o f th e m ix tu r e e l u t e d .
E l u t i o n w i th l i g h t p e t r o l e u m - e t h e r (33 I 1 v / v ) gave a s o l i d
( 0 .1 8 g . ) . R e c r y s t a l l i s a t i o n from l i g h t p e t r o le u m ( b . p .
6 0 -8 0 ° ) gave 0 - ( p h e n y l t h i o m e t h y l ) - 2 , 3 , 5 , 6 - t e t r a c h l o r o q u i n o l
( 0 .1 5 g . ) .
Y i e ld : 0 .1 5 g . (25% th e o r y )
m .p . : 115-6°
i . r . : jiax 3 ,4 5 0 ; 1200 , and 750-700 cm"^
n . m . r . 2 . 5 X ( 5 h y d ro g en m u l t i p l e t )
4 . 4 X (2 h y d ro g en s i n g l e t )
A n a l y s i s 1 Pound: C ,4 2 .2 0 ; H, 2 .0 2 ; C l , 8 .5 3 ;
S, 8.41%, CigHsCl^^OgS r e q u i r e s C, 4 2 .2 5 ; H, 2 .2 0 ;
C l , 8 .6 5 ; S, 8.65%
Mass sp e c tru m : m/e M"̂ 368 (C l = 3 5 )
M+-123, 245 (01 = 35 )
E l u t i o n w i th l i g h t p e t r o l e u m - e t h e r (25 I I ' v / v ) gave
2 , 3 , 5 , 6 - t e t r a c h l o r o q u i n o l (0 .0 8 g . ) , m .p . 230-1° ( l i t ^ ° ° m .p .
2 3 2 ° ) .
105
I r r a d i a t i o n o f a Benzene S o l u t i o n o f T e t r a c h l o r o - p - b e n z o
qu inon e c o n ta in in g : N - ( o - c h i o r oph en y l ) g l y c i n e .
A benzene s o l u t i o n ( l6 0 m l . ) o f t e t r a c h l o r o - p - b e n z o -
q u ino ne (0 .4 9 g . ) c o n t a i n i n g N - (o - c h lo ro p h e n y ] ) g ly c in e ,(0 .3 7 g . ),
was i r r a d i a t e d u n d e r n i t r o g e n , w i th th e H anov ia r e a c t o r , f o r
f o u r h o u r s , t o g iv e a 98% y i e l d o f c a rb o n d i o x i d e . The
s o l u t i o n was e v a p o r a t e d and th e r e s i d u e c h ro m a to g ra p h e d on
s i l i c a (30 g . ) . E l u t i o n w i th l i g h t p e t r o l e u m - e t h e r (30 I 1
v / v ) gave t e t r a c h l o r o - p - b e n z o q u i n o n e ( 0 .3 g . ) , i d e n t i f i e d by
i . r . s p e c t r o s c o p y . E l u t i o n w i th l i g h t p e t r o l e u m - e t h e r
(20 : 1 v / v ) gave 2 , 3 , 5 , 6 - t e t r a c h l o r o q u i n o l ( 0 .1 g . ) , m .p,
231-2° ( l it .^ °® m .p . 232° ) . The am ines p ro d u c e d i n t h e
r e a c t i o n re m a in e d a d s o rb e d t o t h e colum n. T h e i r y i e l d s were
d e te r m in e d by g . l . c . a n a l y s i s on th e r e a c t i o n m ix tu r e ( s e e
T a b le 1 0 ) .
I r r a d i a t i o n o f a Benzene S o l u t i o n o f 9 ,1 0 -A n th ra g u in o n e
c o n t a i n i n g P h e n o x y a c e t ic A c id
A benzene s o l u t i o n ( l6 0 m l . ) c o n t a i n i n g 9 , 1 0 - a n t h r a -
qu inone ( 0 .7 3 g . ) and p h e n o x y a c e t ic a c i d ( 0 .5 3 g . ) was
i r r a d i a t e d f o r tw e lv e h o u r s , w i th th e H anovia r e a c t o r . The
s o l u t i o n was e v a p o r a t e d , and th e r e s i d u e c h ro m a to g ra p h e d on
s i l i c a (30 g . ) . E l u t i o n w i th l i g h t p e t r o l e u m - e t h e r (20 % 1
v / v ) gave 9 ,1 0 - a n th r a q u in o n e ( 0 .6 g . ) , which was i d e n t i f i e d
by i . r . s p e c t r o s c o p y . The o t h e r m a jo r p r o d u c t , a n i s o l e , was
l o s t on e v a p o r a t i o n o f th e b e n zen e s o l u t i o n a n d th e y i e l d o f
a n i s o l e was d e te rm in e d by g . l . c . a n a l y s i s on t h e r e a c t i o n
106
m ix tu re ( s e e T a b le 7 ) .
I r r a d i a t i o n o f a Benzene S o l u t i o n o f 9 .1 0 -A n th ra g u in o n e
c o n t a i n i n g ( P h e n y l t h i o ) a c e t i c A c id
A b enzene s o l u t i o n ( l6 0 m l . ) c o n t a i n i n g 9 , 1 0 - a n t h r a
qu in one ( 1 .0 g . ) a n d ( p h e n y l t h i o ) a c e t i c a c i d ( 0 ,8 g . ) was
i r r a d i a t e d f o r s i x h o u r s , w i th t h e H anov ia r e a c t o r . The
s o l u t i o n was e v a p o r a t e d and th e r e s i d u e was ch ro m a to g ra p h ed
on s i l i c a (35 g . ) . E l u t i o n w i th l i g h t p e t r o l e u m - e t h e r
(20 : 1 v / v ) gave 9 ,1 0 - a n th r a q u in o n e ( 0 .8 g . ) w h ich was
i d e n t i f i e d by i . r , s p e c t r o s c o p y . E l u t i o n w i th l i g h t
p e t r o le u m gave t r a c e s o f m ethy l p h e n y l s u lp h id e ( i d e n t i f i e d by
g . l . c . ) ; how ever, much o f t h i s p r o d u c t was l o s t on e v a p o r a t i o n
o f th e b en zen e s o l u t i o n , and th e y i e l d o f m eth y l p h e n y l
s u lp h id e was d e te rm in e d by g . l . c . a n a l y s i s on t h e r e a c t i o n
m ix tu re ( s e e T ab le 8 ) .
I r r a d i a t i o n o f a Benzene S o l u t i o n o f F lu o re n o n e c o n t a i n i n g
N - ( o - c h i o r o p h e n y l )g l y c i n e
A b e n ze n e s o l u t i o n (80 m l . ) o f f l u o r e n o n e ( 0 .9 g . )
c o n t a i n i n g N - ( o - c h lo r o p h e n y l ) g l y c in e (0 ,9 5 g . ) was i r r a d i a t e d
f o r two h o u r s i n th e R ay o n e t R e a c to r , w i th 350 nm. l i g h t .
A 57? ̂ y i e l d o f c a rb o n d io x id e was o b t a i n e d . From g . l . c . o f
t h e p r o d u c t s o l u t i o n , o - c h l o r o a n i l i n e ( 0 .1 3 g . ) an d a t r a c e
o f N - m e t h y l - o - c h l o r o a n i l i n e were fo rm ed . The p r o d u c t
s o l u t i o n was e v a p o r a t e d and th e r e s i d u e was c h ro m a to g ra p h e d
on a lu m in a (45 g . ) . E l u t i o n w i th l i g h t p e t r o l e u m - e t h e r
107
(50 : 1 v / v ) gave a m ix tu re o f f l u o r e n o n e (0 ,0 6 g , ) and
o - c h l o r o a n i l i n e . An a u t h e n t i c m ix tu r e o f t h e s e two compounds
h ad i . r . and n . m . r . s p e c t r a i d e n t i c a l t o th o s e o f t h e m ix tu re
e l u t e d . E l u t i o n w i th l i g h t p e t r o l e u m - e t h e r (9 1 1 v / v )
gave f l u o r e n o n e ( 0 .0 5 g . ) ( i d e n t i f i e d by i . r . s p e c t r o s c o p y . )
E l u t i o n w i th e t h e r gave f l u o r o p i n a c o l ( 0 .6 0 g . ) , m .p . and
m ixed m .p . 1 9 0 -1 ° .
I r r a d i a t i o n o f a B enzene S o l t u i o n o f X anthone c o n t a i n i n g
P h e n o x y a c e t ic A c id
A b enzene s o l u t i o n (80 m l . ) o f x an th o n e (0 .9 8 g . )
c o n t a i n i n g p h e n o x y a c e t ic a c i d ( 0 .7 6 g . ) was i r r a d i a t e d f o r
3 .5 h o u r s i n th e R ay o n e t r e a c t o r , w i th 350 nm. l i g h t .
An 88% y i e l d o f c a rb o n d io x id e was o b t a i n e d . Prom g . l . c .
o f th e p r o d u c t s o l u t i o n , a n i s o l e ( 0 .1 0 g . ) was fo rm ed . The
p r o d u c t s o l u t i o n was e v a p o r a t e d a n d th e r e s i d u e was ch ro m a to
g ra p h e d on a lum ina (50 g . ) . E l u t i o n w i th l i g h t p e t r o le u m
gave a t r a c e o f a n i s o l e ; t h e b u lk o f t h i s p r o d u c t was l o s t
on e v a p o r a t i o n o f th e p r o d u c t s o l u t i o n . E l u t i o n w i th l i g h t
p e t r o l e u m - e t h e r (30 I 1 v / v ) ^ v e 1 , 2 -d ip h e n o x y e th a n e ( O . l l g . ) ,
m .p , and m ixed m .p , 9 8 ° . E l u t i o n w i th l i g h t p e t r o l e u m - e t h e r
(15 I 1 v / v ) gave x a n th o n e (0 .5 5 g . ) , m .p . and m ixed m .p .
1 7 4°• E l u t i o n w i th e t h e r gave a m ix tu re o f p r o d u c t s w hich
were re c h ro m a to g ra p h e d on a lu m in a (15 g . ) . E l u t i o n w i th
l i g h t p e tro le u m -b e n z e n e (3 t 1 v / v ) gave x a n th o n e ( 0 .2 5 g . ) ,
i d e n t i f i e d a s ab ove .
108
2 . 2 .8 D e te r m in a t io n o f th e R a te C o n s t a n t s f o r D e c a r b o x y la t io n
B e fo re a t t e m p t in g q u en ch in g e x p e r im e n t s , i t was n e c e s s a r y
t o a s c e r t a i n th e ’ optimum' i r r a d i a t i o n tim e f o r e a c h r e a c t i o n
( s u c h t h a t a m e a su ra b le w e ig h t o f b a r iu m c a r b o n a te was
o b t a i n e d w i th s i d e r e a c t i o n s b e in g u n i m p o r t a n t ) . The
i r r a d i a t i o n t im e r e q u i r e d to b r i n g a b o u t 40% c o n v e r s io n o f
th e a c i d was t a k e n , i n e a c h c a s e . A p l o t o f c a rb o n d io x id e
e v o l u t i o n v e r s u s i r r a d i a t i o n tim e was o b t a i n e d f o r e a c h
r e a c t i o n i n v e s t i g a t e d , u s i n g I r r a d i a t i o n P r o c e d u re C.
The r e a c t i o n s were th e n ru n i n t h e p r e s e n c e o f v a r y in g
c o n c e n t r a t i o n s o f q u e n c h e r . N a p h th a le n e was u s e d a s t h e
q u e n ch e r f o r d e c a r b o x y l a t i o n s s e n s i t i s e d by ben zo p h en o n e .
I t does n o t b r i n g a b o u t th e d e c a r b o x y l a t i o n o f th e a c i d s ,
u n d e r th e r e a c t i o n c o n d i t i o n s usedV^ ; i t d o es n o t a b s o rb
a t 350 nm. ( t h e w a v e le n g th o f l i g h t u s e d i n th e r e a c t i o n s
i n v o lv i n g benzophenone) and q uenches a t d i f f u s i o n - c o n t r o l l e d
r a t e *,
9 - N i t r o a n t h r a c e n e was u t i l i s e d a s th e q u e n ch e r f o r th e
d e c a r b o x y l a t i o n s s e n s i t i s e d by t e t r a c h l o r o - p - b e n z o q u i n o n e .
A t 313 nm ,, th e w a v e le n g th o f l i g h t u t i l i s e d , 9 - n i t r o a n t h r a c e n e
h a s n e g l i g i b l e a b so rb a n c e compared t o t e t r a c h l o r o - p - b e n z o -
qu inone ( a t th e c o n c e n t r a t i o n s u s e d ) .
109
( a ) Q uench ing A c t io n o f N a p h th a le n e on th e D e c a r b o x y la t io n
o f N - ( o ~ c h lo r o n h e n v l ) g ly c in e S e n s i t i s e d by Benzophenone
i n A c e t o n i t r i l e S o l u t i o n ,
D e te r m in a t io n o f c a rb o n d io x id e e v o lu t io n *
I r r a d i a t i o n Time ( m i n . )
6
12
21
3 0
W eigh t BaCOa ( g . ) o b t a i n e d
0 .0 1 0 4
0 .0 1 9 8
0 .0 3 5 1
0 . 0 4 9 5
% Y i e l d C arbon D io x id e
8
16
28
4 0
% Y i e ld
C arbon
40% COg
i n 30 minD io x id e
20
10
302 5201 5105
I r r a d ia t i o n Time ( m in .)
110
N a p h th a len e Q uenching*
Wt. n a p h th a le n e
(g . )p e r 10m l, s o l n ,
0
0 ,0 0 3
0,006
0,010
M o l a r i t y o f n a p h th a le n e x 10^
0
2 3 .4
46.8
7 8 ,1
Wt.BaCOa 6o b t a i n e d (g )
i . e .
0 .0 4 7 4 1
0 .0 4 2 3 1 .1 2
0 .0 4 0 4 1 .1 7
0 .0 3 7 2 1 .2 8
(b = 0 .0 4 7 4 g . BaCOa (u n q u en ch ed r e a c t i o n )
1.30
1.20
q1.10
1,00
40 806020
[N a p h th a le n e ] x 10
S lo p e = 38 u n i t s
Prom t h e S te m -V o lm e r e q u a t i o n %
k r = , kd kd-------------- -H —s lo p e X [ik] [a ]
I ll
5 X 10 -
38 X 6 .2 5 X 10
3 X 10-"
* 6 .2 5 X 10“ ^
k r = 2 .1 X 10^ M ^ s e c ” ^
( b ) Q uenching A c t io n o f N a p h th a le n e on t h e D e c a r b o x y la t io n
o f ( p h e n y l t h i o ) a c e t i c A c id S e n s i t i s e d by Benzophenone
i n Benzene S o l u t i o n .
D e te r m in a t io n o f c a rb o n d io x id e e v o lu t io n *
I r r a d i a t i o n Time ( m i n . )
15
30
4 5
60
V/eight BaOOa o b t a i n e d ( g . )
0 .0 3 6 3
0 ,0 5 4 2
0 .0 7 5 5
0 .0 7 8 7
% Y i e ld C arbon D io x id e
30
4 4
61
62
% Y i e ld C arbon
D io x id e
4 0 ^ COg
i n 25 min
20
25 30 4 5 60
I r r a d i a t i o n Time (m in . )
15
112
N a p h th a len e q u en ch in g!
N a p h th a le n e
( g . )
10m l, s o l n .
M o l a r i t y o f n a p h th a le n e
X 10^
Wt, BaCOa o b ta in e d
(g " ) , t g .
0 0 0 .0 5 5 0 1
0 ,0 0 0 5 3 .9 0 .0 3 5 9 1 .5 3
0 ,0 0 2 0 1 5 .6 0 .0 2 3 8 2 .3 1
0 .0 0 3 0 2 3 .4 0 .0 2 0 4 2 ,7 0
0 ,0 0 4 0 3 1 .3 0 .0 1 6 3 3 .3 8
<j> = 0 ,0 5 5 0 g , BaCOo (u n quenched r e a c t i o n )
Î
't’ / A
k
3
2
1
40302010
S lo p e = 800 u n i t s .
[N a p h th a le n e ] x 10
. k r = 1 ,0 X 10^ M ^ s e c
113
( c ) Q uenching A c t io n o f N a p h th a le n e on th e D e c a r b o x y la t io n
o f ( P h e n y l t h i o ) a c e t i c A c id S e n s i t i s e d by Benzophenone
i n A c e t o n i t r i l e S o l u t i o n .D e te r m in a t io n o f c a rb o n d io x id e e v o lu t io n *
I r r a d i a t i o n Time ( m i n . )
25
50
75
100
V/t. BaCOa o b t a i n e d ( g . )
0 .0 2 4 9
0 .0 4 2 3
0 .0 6 0 9
0 .0 7 1 7
% Y i e ld c a rb o n d io x id e
20
35
49
58
/A
/OCarbon
D io x id e40% CQg i n 60 min
20
10025
I r r a d i a t i o n Time (m in . )
N a p h th a le n e q u e n ch in g I
<|> = 0 .0 5 5 0 g . BaCOg ( f o r unq uenched r e a c t i o n )
114
t , N a p h th a le n e M o la r i t y o f Wt. BaCOs ( g . )
( g . )N a p h th a le n e
Llo b t a i n e d
p e r 10m l, s o i n . X 10^
0 0 0 .0 5 5 0 1
0 ,0 0 1 0 7 .8 0 .037 9 1 .4 5
0 ,0 0 3 0 2 3 .4 0 .0 2 2 7 2 .4 2
0 ,0 0 4 5 3 5 .2 0 .0 1 8 8 2 .9 3
0 ,0 0 6 0 4 6 .9 0 .0 1 6 0 3 .4 4
î
+ / f
k
3
2
1
40 5020 3010
[ N a p h th a le n e ] x 10
S lo p e = 550 u n i t s .
k r = 1 .4 5 X 10 m“ \ s e c " ! .
115
(d ) Quenching: A c t io n o f N a p h th a len e on th e D e c a r b o x y la t io n
o f S " ( n - B u t y l t h i o ) a c e t i c A c id S e n s i t i s e d by Benzophenonei n Benzene S o l u t i o n .
D e te r m in a t io n o f c a rb o n d io x id e e v o l u t i o n I
I r r a d i a t i o n Time ( m i n . )
30
50
65
80
Wt. BacOs o b t a i n e d ( g . )
0 .0 3 8 9
0 .0 5 5 8
0 .0 6 2 9
0 .0 6 8 5
% Y ie ld C arbon D io x id e
32
45
51
56
60
40
% Y i e ld 35 C arbon
DioxidOgQ
35 40 60 8020
I r r a d ia t io n Time ( m in . )
116
N a p h th a len e q u en ch in g *
Wt. N a p h th a le n e
( g . )p e r 10m l. s o l n .
0
0 .0 0 0 2
0 .0 0 0 6
0 .0 0 1 0
0 .0 0 1 5
M o la r i t y o f N a p h th a le n e
x l O ^
0
1 . 6
4 . 7
7 .8
1 1 .7
Wt. BaCOa (g , ) o b t a in e d
i . e .
0 .0 4 3 5
0 .0 3 8 4
0.0352
0 .0 3 0 9
0 .0 2 8 3
1
1 .1 3
1 .2 4
1 .4 3
1 .5 4
4 /4
1.2
1.0
6 84 12102
[N a p h th a le n e ] x 10 -»
^ = 0 .0 4 3 5 g . BaCOg ( f o r unquenched r e a c t i o n ) .
S lo p e = 510 u n i t s ,O
k r = 1 .6 X 10 M . s e c . .
117
( e ) Q uenching A c t io n o f N a p h th a le n e on th e D e c a r b o x y la t io n
o f P h e n o x y a c e t ic A c id S e n s i t i s e d by B enzonhenone. i n
Benzene S o l u t i o n .
D e te r m in a t io n o f c a rb o n d io x id e e v o l u t i o n I
I r r a d i a t i o n Time ( m i n . )
Wt, BaCOg o b t a i n e d ( g , )
% Y ie ld Carbon D io x id e
25
56
90
120
0 .0 2 1 9
0 .0 3 6 2
0 .0 4 7 3
0 .0 5 2 7
18
29
38
43
% Y ie ldCarbonD io x id e "dr 30^ COg i n 60 min
20
10
60 1009030
I r r a d ia t io n Time ( m in . )
118
N a p h th a len e q u en ch in g %
W t . N a p h th a le n e ( g . ) ( x 10 ^)
p e r 10m l. s o l n .
0
25
75
125
200
M o la r i t y N a p h th a le n e
(x 10^)
0
1 .9
5 .8
9 . 7
15.6
Wt.BaCOaCg.)o b t a i n e d
0 .0 3 8 5
0 .0 3 3 7
0 .0 3 1 4
0 .0 2 82
0 .0 2 5 2
1
1 .1 4
1 .2 3
1 .3 7
1 .5 3
Î
k /
.6
1 . 4
1.2
1.0
15105
1.2 _
[N a p h th a le n e ] x 10^
^ = 0 .0 3 8 5 g . BaCOo (unq uenched r e a c t i o n ) .
S lop e = 3 ,6 0 0 u n i t s ,J » - lk r = 1 . 7 X 10 M s e c -1
119
( f ) Q.uenchinp; A c t io n o f 9 -N itr o a n th r a c e n e on th e
T e tra c h lo ro -p -b e n z o Q u in o n e i n Benzene S o l u t i o n .
D e te r m in a t io n o f c a rb o n d io x id e e v o l u t i o n !
I r r a d i a t i o n Time W eigh t BaCOg % Y i e ld( m in , ) o b t a i n e d ( g . ) Carbon D io x id e
30 0 .0 1 3 5 11
60 0 .0 2 0 9 17
75 0 .0 2 7 2 22
90 0 .0 3 6 9 30
% Y ie ld C arbon D io x id e
20
30?c COg i n 90 min
10
60 9030
I r r a d i a t i o n Time ( m i n . )
120
9 “N itr o a n th r a c e n e Q uenching ( i r r a d , tim e = 90 m i n . ) l
\ ' / t , 9 ~ n i t r o a n t h r a c e n e ( g , ) M o la r i t y of* V/t.BaCÛQ1 m l. s o l n . 9 -N i t r o a n t h r a c e n e
(x 10^)o b t a i n e d (g . ) i . e . <|)g
0 0 0 .0 3 4 6 1 .0 0
0 .0 1 4 4 .8 0 .0 2 4 3 1 .4 2
0 .0 2 8 9 .7 0 .0 1 8 6 1 .8 6
0 .0 3 1 3 4 .5 0 .0 1 3 2 2 .6 2
= 0 . 0346g . BaCOs (u nquenched r e a c t i o n ) .
3 .0 0
2 . 0 0
1.00
1208060 10020
[ 9 - n i t r o a n t h r a c e n e ] x 10
S lop e = 115 u n i t s .
= 6 .9 6 X 10^ m” ^ . s e c
121
(g ) Q uenching A c t io n o f 9 ~ N i t r o a n th r a c e n e on th e D ecarboxy
l a t i o n o f ( P h e i ]y l th io ) a c e t i c A c id S e n s i t i s e d by
T e tra c h lo ro ~ p ~ b e n z o q u in o n e i n B enzene S o l u t i o n .
D e te r m in a t io n o f Carbon D io x id e e v o lu t io n *
I r r a d i a t i o n Time (m in. )
W eight BaCOg o b t a i n e d (g , )
% Y i e l d C arbon D io x id e
30
60
90
120
0 .0 1 4 8
0 .0 2 7 1
0 .0 3 4 7
0 .0 5 3 2
12
22
29
43
/OC arbon
43% COg i n 120 min20
10
12060 9030
I r r a d i a t i o n Time ( m i n , )
9 “N itr o a n th r a c e n e Q uenching ( i r r a d , t im e = 120 m i n . ) I
122
. 7 t , 9 - n i t r o a n t h r a c e n e ( g , ) M o la r i t y o f \7t,BaC0ap e r 10 m l. s o l n . 9 - N i t r o a n t h r a c e n e o b t a i n e d
(x 1 0^ ) (g . ) i . e .
t /4>
0
0,01
0 . 0 2
0 .0 3
0
4 4 .8
8 9 .7
1 3 4 .5
0.0510
0.0442
0 .0 3 9 1
0 .0 3 4 2
1.00
1 .1 5
1 .2 9
1 .4 9
^ = 0 .0 5 1 0 g . BaCOs (unquenched r e a c t i o n ) .
1.0
0 . 5 14012060 80 10020
[ 9 - n i t r o a n t h r a c e n e ] x 10
S lope = 36 u n i t s .
' . k = 2 .2 0 X 109 s e c “ ^ .
123
2 ,2 ,9 i iC t ln o m e try - D e te r m in a t io n o f L ig h t I n t e n s i t y
( l ) u s e d i n M e c h a n i s t ic S t u d i e s I n v o l v i n g B enzophenone .
A benzophenone - b e n z h y d ro l a c t i n o m e t e r was u s e d ,
We have t h a t I
a c t = .^°„^d.l,sapp. (,)
I
Where, * th e quantum y i e l d f o r d i s a p p e a r a n c e o f
benzophenone , ^^^d isapp * t h e r a t e o f d i s a p p e a r a n c e o f
benzophenone , e x p r e s s e d i n m o is . / l i t r e / s e c . , and *1* i s th e
l i g h t i n t e n s i t y ( e x p r e s s e d i n q u a n t a / L i t r e / s e c , ) ,
D e te r m in a t io n o f
Benzene s o l u t i o n s (10 m l) , w hich were 6 ,2 5 x 10 M i n
benzophenone and b e n z h y d r o l , were i r r a d i a t e d ( u s in g
I r r a d i a t i o n P ro c e d u re C) f o r v a r y i n g l e n g t h s o f t im e , u s i n g
350nra, lam p s . The s o l u t i o n s were c o n ta in e d i n P y re x t u b e s .
The a b so rb a n c e o f benzophenone was m easu red a f t e r i r r a d i a t i o n .
I r r a d i a t i o n Time ( m i n . ) A bso rbance
0 1 .1 12
3 . 5 1 .0 1 2
5 0 .9 5 6
8 0 .8 6 0
1 0 .5 0 .8 0 5
124
-2N .B . 6 , 2 3 X 10 M benzophenone = 1 ,1 1 2 A b sorb ance-2
3 .0 0 X 10 M benzophenone = 0 .8 9 0 A b so rb an ce
1.1
1.0
A bsorbance
0 . 9 -
k 6 82 1210
I r r a d i a t i o n Time ( m i n . )
From th e s lo p e o f th e g ra p h .19
[Bj = 1 .6 9 3 X 10 m o l s . / l i t r e / s e c , ̂ • 'd isa p p .
D e te r m in a t io n o f a c t
(|) was d e te rm in e d from t h e S te m -V o lm e r e q u a t i o n
i a c ta c t
samp1 +
•• W
w h ere . * 9 i s th e quantum y i e l d , f o r d i s a p p e a r a n c e o f' * a c t
125
benzophenone , o f a c t i n o m e te r ( c o n s t a n t b e n z h y d ro l c o n c e n t r a
t i o n i . e . 6 .2 5 X 10” ^M),
* ^ samp* t h e quantum y i e l d , f o r d i s a p p e a r a n c e o f
benzop henon e , o f sam ple s o l u t i o n s ( v a r i a b l e b e n z h y d ro l
c o n c e n t r a t i o n ) ,
and i s th e c o n c e n t r a t i o n o f b e n z h y d r o l .
As we a r e com paring two quantum y i e l d s , e q u a t io n
can be e x p r e s s e d as%
- A a c ta c t
- A samp
1 +
where Aq i s t h e i n i t i a l a b s o rb a n c e o f b en zo phen one ,
A a c t t s th e a b s o rb a n c e o f benzophenone f o r th e a c t i n o
m e te r s o l u t i o n , a f t e r i r r a d i a t i o n ,
and A i s th e a b so rb a n c e o f benzophenone f o r th e sam ple samps o l u t i o n s , a f t e r i r r a d i a t i o n .
H ence, a p l o t o f An — Aa c t
An — A samp
v e r s u s
[B H ]
w i l l g iv e <|> from i t s i n t e r c e p t .
P ro c e d u re I Benzene s o l u t i o n s (10 m l . ) , c o n t a i n i n g
benzophenone ( 6 .2 5 x 10 ) a n d b e n z h y d ro l ( v a r i a b l e c o n c e n t r
a t i o n ) , were i r r a d i a t e d f o r 5 m i n . , ( t a k e n a r b i t r a r i l y ) , u s i n g
i r r a d i a t i o n p ro c e d u re C. S o l u t i o n s were c o n ta in e d i n
126
P y re x tu b e s and th e a b s o rb a n c e o f benzophenone was m easu red
a f t e r i r r a d i a t i o n .
B e n z h y d ro l C o n c e n t r a t i o n [BH]
(x 10^ )
1 '^samp ■ ^“'^samp ^ “^ a c t
[BH] Aq
25 40 1 .0 1 2 100 1 .5 6
40 25 0 .9 7 9 133 1 .1 7
50 20 0 .9 7 5 137 1 .1 4
6 2 .5 16 0 .9 5 6 156 1 .0 0
100 10 0 .9 2 4 188 0 .8 3
A q = 1 .1 1 2
\ o t = 0 -9 5 6
Ao-Üa c t
jAq "“A s amp
1 . 8
1 .4
1.0
0 . 6
40302010
1
[BH]
127
From th e i n t e r c e p t o f th e p l o t , ^ ^ c t “ 0*56
S u b s t i t u t i n g i n e q u a t i o n (\) ;
I = 1 .6 9 5 X 10^9
0 .5 6
L i g h t I n t e n s i t y = 3 .0 2 8 x 10^^ q u a n t a / l i t r e / s e c ,
128
CHAPTER 3
PHOTOINDUCED DECARBOXYLATION OF
CARBOXYLIC ACIDS SENSITISED BY
Q-UINOXALINES.
129
3 .1 R e s u l t s and D i s c u s s io n
3 . 1 . 1 PreliMnapy D e c a r b o x y la t io n S t u d i e s
3%I t h a s b e e n shown by N oyori e t a l '" ' ( s e e S e c t i o n 1 ,2 )
t h a t c e r t a i n b e n z o p y r i d in e s , e . g . a c r i d i n e , can b r i n g a b o u t
th e p h o t o d e c a r b o x y l a t i o n o f c a r b o x y l i c a c i d s .
Some p r e l i m i n a r y s t u d i e s have shown t h a t a c l a s s o f
s i m i l a r compounds, i . e . q u i n o x a l i n e s , a re a l s o c a p a b le o f
s e n s i t i s i n g th e d e c a r b o x y l a t i o n o f v a r i o u s c a r b o x y l i c a c i d s .
The b a s i c q u in o x a l in e u n i t i g a s f o l l o w s , and i s num bered
a s i n d i c a t e d ;
The q u i n o x a l i n e s u s e d i n t h e s e s t u d i e s w e re ;
1 ) 2 , 3 - D ip h e n y lq u in o x a l in e
2) 2 , 3 - D im e th y lq u in o x a l in e
3 ) P h e n a z in e
N
NP h e n a n th r o [ 9 , 1 0 - b ] q u in o x a l in e
N
N
130
The y i e l d s o f c a rb o n d io x id e from th e d e c a r b o x y l a t i o n o f
N - ( o - c h i o r o p h e n y l ) g l y c i n e , ( p h e n y l t h i o ) a c e t i c a c i d , phenoxy
a c e t i c a c i d , p h e n y l a c e t i c a c i d , and S - ( n - b u t y l t h i o ) a c e t i c
a c i d , s e n s i t i s e d by th e above q u i n o x a l i n e s i n b en zen e s o l u t i o n ,
a r e g iv e n i n T a b le 1 8 ,
3 . 1 . 2 . P r o d u c t S tu d ie s
Y ie ld s o f S u b s t i t u t e d H y d ro ca rb o n s
By a n a lo g y w i th th e d e c a r b o x y l a t i o n s s e n s i t i s e d by
c a rb o n y l compounds, i t a p p e a re d l i k e l y t h a t an im p o r ta n t
p r o d u c t from d e c a r b o x y l a t i o n o f a c i d s , o f ty p e RXCHgCOgH,
s e n s i t i s e d by q u i n o x a l i n e s , were s u b s t i t u t e d h y d r o c a r b o n s , o f
type RXCH3 , The d e c a r b o x y l a t i o n o f p h e n o x y a c e t ic a c i d
s e n s i t i s e d by a c e n a p h t h o [ l , 2- b ] q u i n o x a l i n e , p h e n a z in e ,
p h e n a n t h r o [9 , 10- b ] q u i n o x a l i n e , and 2 , 3 - d i p h e n y l q u in o x a l in e
was i n v e s t i g a t e d . The y i e l d s o f a n i s o l e o b t a i n e d a r e g iv e n
i n T ab le 19 .
The r e s u l t s show t h a t a n i s o l e i s n o t a m ajo r r e a c t i o n
p r o d u c t . By a n a lo g y w i th t h e d e c a r b o x y l a t i o n s s e n s i t i s e d
by a c r i d i n e and r i b o f l a v i n ^ , i t i s p r o b a b le t h a t
a d d u c ts a r e fo rm ed , w i th t h e q u i n o x a l i n e s , t h u s a f f o r d i n g low
y i e l d s o f s u b s t i t u t e d h y d ro c a r b o n s , e . g . a n i s o l e from
p h o t o l y s i s o f p h e n o x y a c e t ic a c i d , A d d u c ts were s o u g h t a f t e r
by column c h ro m a to g ra p h y .
131
ü•HrH
o€COÜ<Ho(0
o•H
drHOco
s(DNtiQ)
m
<HofUo
•H+>CO•H
COJhPh
e. 6
-d•H«oR
ggCOO<HO
RO<Düd<DCQ
Sp<
0XI+3
d•H
CD
♦Hü
<
ü•H+30ü 'dCO •HH ü
d<
1R
1O•HXJHJ *d
•H(—1 O
CO-Pd üm •H1 P
0ü
1 roCD
"ü•HP>0ü0 d>? •HK üQ Cd0xjPh1
do •H•H üXI COp>rH ü>ï •Hd P0 0xî üR CO'—'
S1 •HO üd t>5o rHrH bOXîü HO &
01 XîR
CM
S '
00r -
rHrH
m
r -CM
i ï
MD< o
M
CT\CM
r-m
voHt
00CM
CT\m
00xj-
m00
rH00
mM
S
m
CT\00
CM00
m 1 0 0 t—1 0d d d R drH JO •H •H 1 •H0 1 rH rH O rH
•H CM CO 0 rH 0M 1 X M 1
rH O H O en O rH
Od
•H & dp o d*H
0 0 X î d 0 d d d 0 PrH P CT* X ! xî cy* d 0
X î R p •H e0 R •H d N •H
(—1 çq ? 0 0 R,Q d d d 1
nCO 0 0 0Eh u Jd XI
< CM R R CM
§•HrH
MOd
•H
&
0 0S e•H pP p
d do o•H •HP P0 0
•H Pd d0 0d dd d
•H p, ,
d d•H •HS so orH m
1 1m mCM CM
CM CM
d do o•H pP pO ü0 0
CD CD
0 00 00 0
----- '— "
d d0 00 0d d
< ;
0 0d dd dd d0 0ü üo od dR Rd do Op Pp p0 0
P Pd d0 0d dd d
H H
H -
132
I—I0 I—IR0Eh
dOPP0
dXÎP xj- x t Xt x td 0O 0 e d
d d p o0 d Eh px: M pR d<H poo d
00 P •d 0 po P Bp 0pd , ■+* rd â1—1 0 0 0o 0 P P 1CO d Ü d x t O xt p •
p 0 P 1—1 d0 rH d m 0d 0 d R • p0 X O O CM 0N o Ü 1—1d d CM0 ppq d d 0 d O
CÎ? P o X>R p o p do 0 0 O m m p 0o p p • • • 0 0
>H d P CM o 0 00 <: CO dd Ü do d 0p 0 0 pp 0 0 0 00 0 d ^ " 0P d •H
<Hd R <H M d0 o O 0 Od 0 P 0d XÎ d fi d PH p P VD xf o d
0 d CM CM P pq de d p o oo •H >H 0 Bd d d 0R 0 d
Ü d 00 0 XÎ1—1 0 0 pO 0 d o0 d p d dP •H rH R od P 0
d< 0 X dX 0 g o 0<H o d d p 0o dp
•HP p
dp0 0
R0 0 d 0 Pdd d p X d1—1 p 1—1 o R 0 P
0 p R d 1 d 0p 0 1 p O d p>H X CM d P H >Ho
d P P cn 4 -Ojdpjd
ts
5R•H?
CM
0 dg
S
1
d•HNsR
133
D e te r m in a t io n o f P r o d u c t s by Column C h ro m ato g rap h y .
The p r o d u c t s from th e d e c a r b o x y l a t i o n o f p h e n o x y a c e t ic
a c i d s e n s i t i s e d by a c e n a p h t h o [ l , 2- b ] q u i n o x a l i n e and p h en an
t h r o [9 , 1 0 -b ] q u in o x a l i n e , i n benzene s o l u t i o n u n d e r n i t r o g e n ,
w ere i n v e s t i g a t e d by column c h ro m a to g ra p h y . I n b o th c a s e s
th e q u in o x a l in e was r e c o v e r e d i n h ig h y i e l d ; how ever, some o f
t h e q u in o x a l in e f r a c t i o n s , o b t a i n e d from th e p h o t o l y s i s o f
a c e n a p h t h o [ l , 2- b ] q u i n o x a l i n e , were c o n ta m in a te d w i th a n o th e r
p r o d u c t ( a s i n d i c a t e d by a s l i g h t lo w e r in g o f t h e m e l t in g
p o i n t and th e p r e s e n c e o f e x t r a a b s o r p t i o n s , i n th e i n f r a r e d
sp e c tru m a t 1252, 745 , and 685 cm ^ ) . The s p e c t r a l d a t a
i n d i c a t e d t h a t th e ' im p u r i ty * c o n ta in e d th e PhOCHg- u n i t ;
t h i s was p r o b a b ly due t o an a d d u c t o f ty p e I w hich , h a v in g
s i m i l a r e l u t i o n p r o p e r t i e s t o th e s t a r t i n g q u i n o x a l i n e ,
c o u ld n o t be s e p a r a t e d from th e l a t t e r by c h ro m a to g ra p h y .
I t i s l i k e l y t h a t th e v e ry low y i e l d o f *adduct* o b t a i n e d i s
due t o i t s d e c o m p o s i t io n on th e colum n.
I n o r d e r t o o b t a i n a b e t t e r m a t e r i a l b a la n c e b e tw ee n
r e a c t i o n p r o d u c t s and s t a r t i n g m a t e r i a l s , t h e p r o d u c t s from
r e a c t i o n s o f a c e n a p h t h o [ l , 2 - b ] q u i n o x a l i n e w i th p h e n o x y a c e t ic
a c i d , ( p h e n y l t h i o ) a c e t i c a c i d , an d N - ( o - c h i c r o p h e n y l )g l y c i n e .
134
and p h e n a n t h r o [ 9 , 1 0 - b ] q u i n o x a l in e w i th p h e n o x y a c e t ic a c i d and
( p h e n y l t h i o ) a c e t i c a c i d , i n th e p r e s e n c e o f a i r , were
i n v e s t i g a t e d by column c h ro m a to g ra p h y . The r e s u l t s a re
shown i n T ab le 20 ,
I n a l l c a s e s th e dem e th y la te d p r o d u c t , RXH, was fo rm ed
i n good y i e l d , A p r o b a b le r o u t e t o t h i s p r o d u c t , i n v o l v i n g
a r a d i c a l m echanism , i s a s f o l lo w s !
RXCHgCOsH + Q RXCHg + cjî + COg . , . l
RXCHg + Og RXCHgOO* . . . 2
RXCHg OcT + ^ RXCHg OOH + Q . . . 3
RXCHg OOH R X C ^ j j . . . 4
R X C ^ . . . 5H
(where **q '* i s th e q u i n o x a l i n e ) .
The i n t e r m e d i a t e I I was n o t i s o l a t e d from th e s e r e a c t i o n s .
The p r o d u c t i o n o f t h i o a n i s o l e i n r e a c t i o n s i n v o lv i n g (p h en y -
l t h i o ) a c e t i c a c i d p r o b a b ly o c c u r s v i a th e f o l l o w in g h y d ro g en
a b s t r a c t i o n r e a c t i o n !
PhSH + PhSCHg PhS* + PhSCHg . , . 6
A s th e r e a c t i o n p r o c e e d s , th e c o n c e n t r a t i o n o f th io p h e n o l
(w hich i s a good h y d ro g en d o n o r ) i n c r e a s e s , and t h e r e a c t i o n
d e p i c t e d i n e q u a t io n 6 i s f a c i l i t a t e d . F o rm a tio n o f a n i s o l e
135
ü•H
gXoX I0COü<HOen0O
•HP0
rHO
CO0
0 •H0 <0N0 O0Ph 0
O«H 0O 0ra0 0O 0
•H APCO 0
1—1 X !
b pMO 0
X I •H0CO raü 00 0A •H
PG roO %0 oA 0
•H"d 0■ 0
0P bCCO 0
p •HX I 0o •H
COw Pp 0ü O0 Üdo0A d
•H
A ü
O <;î>50COGG000
OCvJ
(DI—I
B
g•H
CO•H'dsM
<HOCO
rH<D
•H
TZJrH0
•H
S•H I—I
id
•H0
•Hü
x;
i•HEh
CO -p ü 0fd "doÎHPHP40Xl-PO
«• HXo
g■gCOü
•dg>oü0
‘3? Ph
0 •H (—IX§
•H
a
m
0•HCO-P
O
dIz
COM
C\J
rHi0
&0O
üI
0
1
ICM
O
gA
00ü
m
0•Hü> ï
*3)I
0•HrH
X0
•H
&
r-00
grH
I
rQI
CM
m CO00
ü•H•P0üCO
0•Hr—I
8O
•S&
ü•H■P
8CO&0 0
1
CM
OXî+ a
A
00ü
<
O•Hx î-p
0
g
•HrH
I•H
&
d•H■P0üCO
L T i
-0
bS m bO bO bO bObO bO xt -d" CM G\ rn AMO O 1—1 o O o P1—1 O
• O o o O o OO O
0 010 S K ffi d tdCO CO O o CO g oXI XI XI X: XI cg XIA A A A A
gA
m m O CP» 1—1 mrn rH 00 00 M p 00
h- r- m or- r- 00 MO
m00
ü•H■P0ü
I0
I
I0üg■P
XI XI
o op 0 p 0
0 0CPv P cr\ P
1—1 Po CO o 00 X 0 XXI o XI Op 0 p 00 •H 0 •HCO 0 0 00 P 0 et0 0XI XIA A
•d0■pCOrH
Iü0tJod•HüCO
«HO
■p§BCO
gnd00CO
X I
-diH0
•H>H
136
from r e a c t i o n s o f p h e n o x y a c e t ic a c i d p r o b a b ly o c c u r s i n an
a n a lo g o u s m anner.
The h ig h y i e l d s o f q u in o x a l in e o b ta in e d a r e due t o th e
r e a c t i o n d e p i c t e d i n e q u a t io n 3 , and i t s r e g e n e r a t i o n from th e
re d u c e d fo rm , QH , a s f o l lo w s I
QH + Og Q + HOr
3 . 1 .3 The Mechanism o f D e c a r b o x y la t io n
Due t o a l a c k o f a v a i l a i b l e t im e , a d e t a i l e d m e c h a n i s t i c
s tu d y c o u ld n o t be c a r r i e d o u t , on th e s e r e a c t i o n s . I t i s
p r o b a b le t h a t th e mechanism in v o lv e s a n i n i t i a l p r o t o n33-t r a n s f e r ( a s s u g g e s te d by N oyori e t a l , f o r d e c a r b o x y la
t i o n s s e n s i t i s e d by b e n zo p y r id in es) t o g iv e an e x c i t e d com plex ,
I I : ; :
RC02H
I I I
The complex I I I can th e n b r e a k down by two p o s s i b l e p a th w a y s ,
i , e , v i a r a d i c a l s o r v i a i o n s , %
V ia R a d ic a l s %
137
p r o d u c t s «<-
V ia Io n s I
%
e l e c t r o nr W
H 3OgCR
t r a n s f e r—
U1H
OgCR
rTH
-CO.
—CO2
p r o d u c t s
I f th e r e a c t i o n o c c u r s v i a th e i o n i c m echanism , a p o s s i b l e
r o u te t o th e p r o d u c t RXH (T a b le 20) i s a s f o l lo w s I
RXCHg COg H + Q RXCHg + COg + QH
R X C I^
RXCHg"
+ Og RXCHg + Og
+ Og RXCHg 00* e t c .
:<s>
F u r t h e r s t u d i e s a r e r e q u i r e d t o d e te r m in e which o f t h e a l t e r n
a t i v e mechanisms i s o p e r a t i n g .
138
3*2 E x p e r im e n ta l
3 . 2 . 1 G e n e ra l D e t a i l s
The i n s t r u m e n t a t i o n , r e a g e n t s u s e d , and m ethod o f
c a rb o n d io x id e e s t i m a t i o n a r e th e same a s d e s c r i b e d i n
S e c t i o n 2 , 2 , G a s - l i q u i d c h ro m a to g ra p h ic a n a l y s e s were
c a r r i e d o u t a s o u t l i n e d i n S e c t i o n 3 . 2 , 3 .
3 . 2 . 2 S t a r t i n g M a t e r i a l s
102.P h e n a z in e , m .p . 176-7® l i t , m .p . 1 7 1 ° , was r e c r y s t a l l
i s e d from e t h a n o l - w a t e r (50 * 50 v / v ) . The o t h e r q u in o x a l in e s
were p r e p a r e d , from th e c o r r e s p o n d in g o c -d ik e to n e s , by th e
method o f Vogel u s i n g th e g e n e r a l r e a c t i o n *
O ^ R
O ^ R
Method* The d ik e to n e ( 0 ,0 5 m o le s) was d i s s o l v e d i n a l c o h o l
and an a l c o h o l i c s o l u t i o n o f o -p h e n y le n e d ia m in e (0 ,0 5 m o les)
was a d d ed . The m ix tu re was h e a t e d on a w a te r b a t h , f o r
15 m in u te s , c o o le d , d i l u t e d w i th w a te r , f i l t e r e d , and th e
s o l i d o b t a i n e d r e c r y s t a l l i s e d from w a t e r - a l c o h o l (50 I 50 v / v ) .
The f o l lo w in g q u i n o x a l i n e s were p r e p a r e d !
139
103( i ) 2 ,3 - D i p h e n y l q u i n o x a l i n e , m .p . 1 2 2 -4 ° , l i t m .p . 1 2 4 ° .
The a - d i k e t o n e u s e d was b e n z i l .
( i i ) P h e n a n th r o [ 9 ,1 0 - b J q u i n o x a l i n e , m .p . 2 2 5 - 6 ° , l i t
m .p. 217° . The a - d i k e to n e u s e d was 9 , 1 0 - p h e n a n th r a q u in o n e .
( i i i ) A c e n a p h t h o [ l , 2- b ] q u i n o x a l i n e , m .p , 239- 241° , l i t .^ °*
m .p . 241° . The a - d i k e t o n e u s e d was a c e n a p h th e n e q u in o n e .
( i v ) 2 , 3 -D im e th y lq u in o x a l in e , m .p . 105-6° l i t ,^ ^ ^ m .p . 1 0 6 ° .
The a - d i k e t o n e u s e d was b i a c e t y l .
3 . 2 . 3 A n a ly s e s by Gas L iq u i d C hrom atography
A n a ly se s were c a r r i e d o u t u s i n g a Pye Unicam 104
C hro m atog raph . The method o f d e t e r m i n a t i o n was a s d e s c r i b e d
i n S e c t i o n 2 . 2 . 2 (w i th n a p h th a le n e b e in g u s e d a s a n i n t e r n a l
s t a n d a r d ) . A g l a s s column p a c k e d w i th 10% E30 on 100-120
mesh a c id -w a s h e d an d s i l a n i s e d C e l i t e was u t i l i s e d f o r th e
d e t e r m i n a t i o n o f a n i s o l e , p h e n o l , t h i o a n i s o l e , t h io p h e n o l ,
and o - c h l o r o a n i l i n e , a t 100° , 100° , 120° , 120° , a n d 140° ,
r e s p e c t i v e l y . The d im e n s io n s o f th e column were 5 f t . % ^ / ^ i n .
3 . 2 . 4 P r o d u c t S t u d i e s
The f o l lo w in g i r r a d i a t i o n s were a l l c a r r i e d o u t i n a
R ayo ne t r e a c t o r e q u ip p e d w i th lam ps g i v in g maximum e m is s io n
a t 350 n m ,.
140
I r r a d i a t i o n o f a Benzene S o l u t i o n o f A c e n a p h t h o r i .2 - b 1 -
q u i n o x a l i n e C o n ta in in g P h e n o x y a c e t ic A c id . Under N i t r o g e n .
A b en zen e s o l u t i o n (40 m l . ) c o n t a i n i n g a c e n a p h t h o [ l ,2 - b ] -
q u in o x a l in e (0 ,6 3 5 g . ) and p h e n o x y a c e t ic a c i d (0 . 38g . ) was
i r r a d i a t e d f o r t h r e e h o u r s u n d e r n i t r o g e n . A 51% y i e l d o f
c a rb o n d io x id e was o b t a i n e d . G a s - l i q u i d c h ro m a to g ra p h ic
a n a l y s i s o f t h e p r o d u c t s o l u t i o n gave a n i s o l e (0 .0 1 5 g . ) .
The s o l u t i o n was e v a p o r a t e d and th e r e s i d u e c h ro m a to g ra p h ed
on a lu m in a (30 g . ) . E l u t i o n w i th l i g h t p e t r o l e u m - e t h e r
(100 I 1 v / v ) gave 1 , 2-d ip h e n o x y e th a n e ( 0 .0 3 g . ) , m .p . 9 5 - 7 ° ,
( l i t . m .p . 9 8 ° ) . E l u t i o n w i th l i g h t p e t r o l e u m - e t h e r
( 2 * 1 v / v ) gave w h i te c r y s t a l s , s e v e r a l f r a c t i o n s o f w hich
were p u re a c e n a p h t h o [ l , 2 - b ] q u i .n o x a l i n e (0 .4 2 g . ) , m .p . 239- 104
40° ( l i t . m .p . 241° ) ; ho w ever, a few o f t h e f r a c t i o n s h ad
m .p , 220- 237° a n d from th e i n f r a r e d sp e c tru m th e y were
p r e d o m in a n t ly a c e n a p h t h o [ l , 2- b ] q u i n o x a l i n e , c o n ta m in a te d
w i th a n o t h e r p r o d u c t w hich gave r i s e t o a d d i t i o n a l p e a k s a t
1 , 2 5 2 , 745, an d 685 cm ^ . . The m ix tu re ( 0 .1 4 g . ) was
c a r e f u l l y re c h ro m a to g ra p h e d on a lu m in a (8 g . ) , b u t s e p a r a t i o n
c o u ld n o t be e f f e c t e d ( e l u t i o n w i th l i g h t p e t r o l e u m - e t h e r
(3 1 1 v / v ) gave r e c o v e r y o f th e m ix t u r e ) .
I r r a d i a t i o n o f a Benzene S o l u t i o n o f P h e n a n t h r o f g . l O - b l -
q u in o x a l in e C o n ta in in g P h e n o x y a c e t ic i \ c i d . U nder N i t r o g e n .
A b en zen e sd luticn (80 m l. ) c o n t a i n i n g p h e n a n t h r o [ 9 ,1 0 - b ] -
q u in o x a l in e ( 0 .7 0 g . ) and p h e n o x y a c e t ic a c i d (0 .3 8 g . ) was
i r r a d i a t e d f o r t h r e e and a h a l f h o u r s u n d e r n i t r o g e n . A 42%
141
y i e l d o f c a rb o n d io x id e was o b t a i n e d . Prom g . l . c . o f th e
p r o d u c t s o l u t i o n , a n i s o l e (0 .0 2 5 g . ) was fo rm ed . The s o l u t i o n
was e v a p o r a t e d a n d th e r e s i d u e c h ro m a to g ra p h ed on a lu m in a
(30 g . ) . E l u t i o n w i th l i g h t p e t r o l e u m - e t h e r (100 I 1 v / v )
gave 1 , 2-d ip h e n o x y e th a n e (0 .0 1 g . ) , i d e n t i f i e d by i n f r a r e d
sp e c t ru m . E l u t i o n w i th l i g h t p e t r o l e u m - e t h e r (8 % 1 v / v )
gave p h e n a n t h r o [9 , 10- b ] q u in o x a l in e (0 .6 1 g . ) , m .p . and
m ixed m .p . 225- 6° .
I r r a d i a t i o n o f a B enzene S o l u t i o n o f A c e n o p h th o [ l .2 - b 1 -
q u in o x a l in e C o n t a i n i n g N - ( o - c h lo r o p h e n v l )g l .vc ine i n th e
P r e s e n c e o f A i r .
A b e n ze n e s o l u t i o n (45 m l . ) c o n ta in g a c e n a p h t h o [ l , 2 - b ] -
q u in o x a l in e (0 .6 3 5 g . ) and N - ( o - c h i o r o p h e n y l )g l y c i n e (0 .4 6 4 g . )
was i r r a d i a t e d f o r t h r e e and a h a l f h o u r s i n th e p r e s e n c e o f
a i r . A 69% y i e l d o f c a rb o n d i o x id e was o b t a i n e d . From
g . l . c . o f th e p r o d u c t s o l u t i o n , o - c h l o r o a n i l i n e (0 .1 6 g . )
was fo rm ed . The s o l u t i o n was e v a p o r a t e d and th e r e s i d u e
c h ro m a to g ra p h e d on a lu m in a (50 g . ) . E l u t i o n w i th l i g h t
p e t r o l e u m - e t h e r (6 Z 1 v / v ) gave t r a c e s o f a brown o i l ; t h e
i n f r a r e d sp e c t ru m o f t h i s p r o d u c t s u g g e s t e d t h a t i t was
o - c h l o r o a n i l i n e , m ost o f t h i s p r o d u c t b e in g l o s t on e v a p o r a
t i o n o f t h e p r o d u c t s o l u t i o n . E l u t i o n w i th l i g h t p e t r o l e u m -
e t h e r (3 1 1 v / v ) gave a c e n a p h t h o [ l , 2- b ] q u i n o x a l in e (0 .5 8 g . )
m .p . and m ixed m .p . 2 4 0 - 1° .
142
I r r a d i a t i o n o f a Benzene S o l u t i o n o f A c e n a p h t h o r i . 2 - b 1-
q u in o x a l in e C o n ta in in g ( P h e n y l t h i o ) a c e t i c A c id , i n th e
P r e s e n c e o f A i r .
A b enzene s o l u t i o n (40 m l . ) c o n ta in g a c e n a p h t h o [ l , 2 - b ] -
q u in o x a l in e (0 .6 3 5 g . ) an d ( p h e n y l t h i o ) a c e t i c a c i d (0 .4 2 g . )
was i r r a d i a t e d f o r t h r e e h o u r s , u n d e r a i r , A y i e l d o f
c a rb o n d io x id e was o b t a i n e d . Prom g . l . c . o f th e p r o d u c t
s o l u t i o n , t h io p h e n o l (0 .0 9 g . ) and t i i o a n i s o l e ( 0 .0 4 g . ) were
fo rm ed . The s o l u t i o n was e v a p o r a t e d and th e r e s i d u e ch ro m a t
o g rap hed on a lu m in a (50 g . ) . E l u t i o n w i th l i g h t p e t r o le u m -
e t h e r (20 I 1 v / v ) gave d ip h e n y l d i s u l p h i d e ( 0 ,0 7 g . ) , m .p.
and mixed m .p . 6 0 - 1 ° . E l u t i o n w i th l i g h t p e t r o l e u m - e t h e r
(7 I 2 v / v ) gave a c e n a p h t h o [ l , 2- b ] q u in o x a l in e (0 .5 5 g . ) , m .p.
and mixed m .p . 240- 1° .
I r r a d i a t i o n o f a B enzene S o l u t i o n o f P h e n a n t h r o f 9 .1 0 - b l -
q u in o x a l in e C o n ta in in g ( P h e n y l th io ) a c e t i c i^c id i n th e
P r e s e n c e o f A i r .
A b e n ze n e s o l u t i o n (45 m l . ) c o n t a i n i n g p h e n a n t h r o [ 9 , 10-b]-
q u in o x a l in e ( 0 .7 0 g , ) and ( p h e n y l t h i o ) a c e t i c a c i d ( 0 .4 2 g . )
was i r r a d i a t e d f o r two h o u r s , i n t h e p r e s e n c e o f a i r . An
85% y i e l d o f c a rb o n d io x id e was o b t a i n e d . Prom g . l . c . o f th e
p r o d u c t s o l u t i o n , th io p h e n o l (0 .0 9 g . ) an d t h i o a n i s o l e
(0 .0 3 g . ) were fo rm e d . The s o l u t i o n was e v a p o r a t e d and th e
r e s i d u e c h ro m a to g ra p h e d on a lu m in a (50 g . ) . E l u t i o n w i th
l i g h t p e t r o l e u m - e t h e r (25 I 1 v / v ) gave d ip h e n y l d i s u l p h i d e
(0 ,0 6 5 g . ) , m .p . and mixed m .p , 61° . E l u t i o n w i th l i g h t
143
p e t r o l e u m - e t h e r (9 Z 1 v / v ) gave p h e n a n t h r o [ 9 , 10- h ] q u in o x a l in e
( 0 .6 3 g . ) , m .p . and m ixed m .p. 225- 6° .
I r r a d i a t i o n o f a Benzene S o l u t i o n o f A c e n a n h th o F1 .2 - b 1 q u in o x
a l i n e C o n ta in g P h e n o x y a c e t ic A c id , i n th e P re s e n c e o f A i r .
A b en zen e s o l u t i o n (40 m l . ) c o n t a i n i n g a c e n a p h t h o [ l , 2 - b ] -
q u in o x a l in e ( 0 .6 3 5 g . ) and p h e n o x y a c e t ic a c i d ( 0 .3 8 g . ) was
i r r a d i a t e d f o r f o u r and a h a l f h o u r s , i n th e p r e s e n c e o f a i r .
A 77/0 y i e l d o f c a rb o n d io x id e was o b t a i n e d . Prom g . l . c . o f
th e p r o d u c t s o l u t i o n , p h e n o l ( 0 .1 4 g . ) and a n i s o l e (0 .0 2 g . )
were fo rm ed . The s o l u t i o n was e v a p o r a t e d and th e r e s i d u e
c h ro m a to g ra p h ed on a lu m in a (50 g . ) . E l u t i o n w i th l i g h t
p e t r o l e u m - e t h e r gave t r a c e s o f a n i s o l e ( i d e n t i f i e d by g . l . c . ) .
E l u t i o n w i th l i g h t p e t r o l e u m - e t h e r ( 3 . 1 ) gave a c e n a p h th o -
[ l , 2 - b ] q u in o x a l in e ( 0 .5 9 g . ) , m .p . and m ixed m .p . 240- 1° ,
I r r a d i a t i o n o f a B enzene S o l u t i o n o f P h e n a n th r o [ 9 . 1 0 - b 1q u in
o x a l i n e C o n ta in in g P h e n o x y a c e t ic A c i d . i n t h e P re s e n c e o f A i r .
A benzen e s o l u t i o n (45 m l . ) c o n t a i n i n g p h e n a n t h r o [ 9 , 1 0 - b ]-
q u in o x a l in e (0 .7 0 g . ) and p h e n o x y a c e t ic a c i d (0 .3 8 g . ) was
i r r a d i a t e d f o r f o u r and a h a l f h o u r s , i n th e p r e s e n c e o f a i r .
A 60% y i e l d o f c a rb o n d io x id e was o b t a i n e d . Prom g . l . c .
o f th e p r o d u c t s o l u t i o n , p h e n o l (0 .1 2 g . ) and t r a c e s o f
a n i s o l e were fo rm ed . The s o l u t i o n was e v a p o r a t e d an d th e
r e s i d u e c h ro m a to g ra p h ed on a lu m in a (50 g . ) . E l u t i o n w i th
l i g h t p e t r o l e u m - e t h e r (9 1 1 v / v ) gave p h e n a n th r o [ 9 , 10- b ] -
q u in o x a l in e (0 . 60g . ) , m .p . and m ixed m .p . 225- 6° .
144
REFERENCES
1 . J .W . Sidm an, Chem. R e v . , 689, (1 9 5 8 ) .
2 . W.G. H e r k s t r o e t e r , A.A, L am ola , and G .S , Hammond,
J . Amer. Chem. S o c . , (1964), 4537 .
3 . J . J . B ohning a n d K. W e is s , J . Amer. Chem. S o c . ,
(1 9 6 6 ) , 8 8 , 2893.
4 . G.N. Lew is and M. K asha , J . Amer. Chem. S o c . ,
(1944), 66, 2100.
5 . G. C ia m ic ia n and P . S i l b e r , B e r . , ( 1 9 0 0 ) , 3 ^ , 2911 .
6 . W.M. Moore and M. Ketchum, J . Amer. Chem. S o c . ,
( 1 9 6 2 ) , 84 , 1 368 .
7 . W.M. Moore, G .S . Hammond, and R .P . F o s s ,
J . Amer, Chem. S o c . , ( 1 9 6 1 ) , 83_, 2789.
8 . A .A . Lamola and G .S . Hammond, J . Chem, P h y s . ,
(1 9 6 5 ) , 4 1 , 2129 .
9 . H . I . J o s c h e k and L . I . G ro s s w e in e r , J . Amer. Chem.
Soc (1 9 6 6 ) , 8 8 , 3261 .
10 . D.G. C rosby and C .S . Tang, J . A g r . Food Chem.,
(1 9 6 9 ) , 1 7 , 1291.
11 , C. W a l l in g , ' ' F r e e R a d i c a l s i n S o l u t i o n ' ' ,
Chap. 9 , W ile y , New Y ork , (1 9 5 7 ) .
12 , M. A n b a r , ' 'A d v a n c e s i n C h e m is try S e r i e s ' ' , No. 50 ,
p . 55, A m erican C hem ica l S o c i e t y , W ash ing to n D .C . ,
( 1 9 6 5 ) .
1 3 . J .D . Marge rum and C .T . P e t r u s i s , J . Amer, Chem. S o c . ,
( 1 9 6 9 ) , 9 1 , 2467 .
145
1 4 . J .D . M argem m , J , Amer. Chem. S o c . , (1 9 6 5 ) , 8 7 .
3772 .
15 . G. V /e tte rm ark , J , P h y s . Chem., (1 9 6 2 ) , 256 0 .
1 6 . H .E . Zimmerman, Advan. P h o to c h e m ., (1 9 6 3 ) , 1 , 203 .
17 . S . B la c k b u rn , B iochem . J . , (1 9 4 9 ) , 4 5 , 579.
18 . G .L . M i l l s , B iochem . J . , (1 9 5 2 ) , 52., 707.
1 9 . B. P o l l a r a and R.W. Von K o r f f , B io ch im . B io p h y s .
A c t a . , ( I 9 6 0 ) , 5 2 , 364 .
20 . D.W. R u s s e l l , B iochem . J . , ( 1 9 6 2 ) , 82 , 8P .
2 1 . D.W. R u s s e l l , J .C h e m .S o c . , (1 9 6 3 ) , 894 .
22 . D.W. R u s s e l l , J . Chem. S o c . , (1 9 6 4 ) , 2829.
23 . R . J . P o l l i t t , Chem. Comm., (1 9 6 5 ) , 262.
24 . D . J . N ead le and R . J . P o l l i t t , J . Chem. Soc . (C ) ,
(1 9 6 7 ) , 1764 .
25. D . J . N ead le and R . J . P o l l i t t , J . Chem. S o c . ( C ) ,
(1 9 6 9 ) , 2127.
26 . 0 . M eth-Cohn, T e t . L e t t s . , (1 9 7 0 ) , 1235 .
27 . P .H . M cFarlane and D.W. R u s s e l l , T e t . L e t t s . ,
(1 9 7 1 ) , 725 .
28 . P .H . M cFarlane and D.W. R u s s e l l , Chem. Comm.,
(1 9 6 9 ) , 4 7 5 .
29 . R.-A. S h e ld o n and J . K . K o c h i , J . Amer, Chem. S o c . ,
(1968), 9 0 , 6688.
3 0 . J . K . Kochi and T.W. B e th e a , J . O rg. Chem.,
(1 9 6 8 ) , 3 2 , 75 .
31 . J .K . K o c h i , R.A. S h e ld o n , and S .S . L and e ,
T e t r a h e d r o n , (1 9 6 9 ) , 2 5 . 1197 .
3 2 . R. N o y o r i , M. K a to , M. K a w a n is i , and H. N o z a k i ,
T e t r a h e d r o n , (1 9 6 9 ) , 2 5 . 1125 .
146
3 3 . F .R , S t e r m i t z , C .C . W ei, and W.H. Huang, Chem. Comm.,
(1968), 482 .
3 4 . G. J a c k s o n and G, P o r t e r , P r o c . Roy. S o c . , ( I 9 6 l ) ,
A 260 , 13 .
33 . W. R ic k a t s o n and T .S . S t e v e n s , J . Chem. S o c . ,
(1 9 6 3 ) , 3960 .
36 . P .R , S t e r m i t z and W.H, Huang, J . Amer. Chem. S o c . ,
(1 9 7 0 ) , 9 2 , 1446.
37 . S .Y . Wang, J . C . N n a d i , and D. G re e n f
Chem. Comm., (1 9 6 8 ) , 1162 .
38 . S .Y . Wang, N a tu r e , L o n d . , (1 9 5 9 ) , 184 . B .A .5 9 .
39 . S .Y . Wang, J . C . N n ad i, and D. G r e e n f e l d .
T e t r a h e d r o n , ( 1 9 7 0 ) , 3913, 2 6 .
4 0 . D. E la d and I . R o s e n th a l , Chem. Comm., (1 9 6 9 ) , 9 0 5 .
41 . R. S a n tu s , C. H e le n e , and M. P t a k , Compt. R e n d . ,
(1 9 6 6 ) , 262D. 2077.
42 . E . J . Baum and R .O .C . Norman, J . Chem. Soc . ( b ) ,
( 1 9 6 8 ) , 227 .
4 3 . R .O .C . Norman and R . J . P r i t c h e t t , J .C hem . Soc . (B ) ,
(1 9 6 7 ) , 9 2 6 .
4 4 . C. W a l l in g and M .J , G ib i a n , J . Amer. Chem. S o c . ,
(1 9 6 5 ) , 82 , 3361 .
4 5 . E . J . Baum, J . K . S . Wan, and J .N . P i t t s j u n . .
J . Amer. Chem. S o c . , ( 1 9 6 6 ) , 8 8 . 2652.
4 6 . R .O .C . Norman and G.K. R adda, P r o c . Chem. S o c . ,
(1 9 6 2 ), 1 3 8 .
4 7 . O .P . J o s h u a and G .E . L e w is , T e t . L e t t s , , ( 1 9 6 6 ) ,
4533 .
147
4 8 . Y. Maki and M, S u z u k i , Chem. Comra., ( I 9 ? l ) , 117 .
4 9 . S . P u j i t a , T . Nomi, and H. N o z ak i , T e t . L e t t s . ,
(1 9 6 9 ) , 3557 .
50. A.W. G a l s to n , P r o c , N a t l . A c a d . , S c i . , U .S . , (1 9 4 9 ) ,
I S , 1 0 .
51 . B. N a th a n so n , M. B rody , S . B rody , and S .B . B ro yde ,
Photochem . P h o t o b i o l . , (1 9 6 7 ) , 6 , 177 .
52 . J . M eyer, Z. B o ta n , (1 9 5 8 ) , 4 6 , 124 .
53. G. O s te r and A,H . Adelman, J . Amer, Chem, S o c . ,
(1 9 5 6 ) , 1 8 , 913 .
54. V/.R. P r i s e l l , C.W* Chung, and C.G. M ack en z ie ,
J . B i o l . Chem. (1 9 5 9 ) , 2^4 , 1297.
55 . W .J . N ic k e r s o n and G. S t r a u s s , J . Amer. Chem. S o c . ,
( I 9 6 0 ) , 82 , 5007.
56. K. Enns and W.H. B u rg e s s , J . Amer. Chem. S o c . ,
(1 9 6 5 ) , 81 , 5766.
57 . S . P a t t o n , J . D a i r y . S o i . , (1 9 5 4 ) , 2 2 , 4 4 6 .
58. P . Byrom and J . H. T u r n b u l l , Photochem . P h o t o b i o l . ,
(1 9 6 7 ) , 6 , 125 .
59 . L .R . T e t h e r and J .H . T u r n b u l l , B iochem . J . , (1 9 6 2 ) ,
82 , 517.
60. P . Byrom and J . H. T u r n b u l l , Photochem . P h o t o b i o l . ,
(1 9 6 8 ) , 8 , 243.
61. G.R. P e n z e r and G.K. Radda, B iochem . J . , (1 9 6 8 ) ,
1 0 9 . 259 .
62. P . Hemmerich, V. M assey, and G. W eber, N a t u r e ,
(1 9 6 7 ) , 211 , 728.
148
63. W.H. W alk e r , P . Hemmerich, and V. M assey,
H e lv . Chim. A c t a . , ( 1 9 6 7 ) , 50, 2269 .
64. A. De Kok and C. V e e g e r , B ioch im , B io p h y s . A c t a . ,
(1 9 6 7 ) , 1 2 1 , 589.
65 . M. B r u s t l e i n a n d P . Hemmerich, P .E .B .S . L e t t s . ,
( 1 9 6 8 ) , 1 , 33 5 .
66 . G.D. ï i 'e a th e rb y and D.O. C a r r , B io ch e m ., (1 9 7 0 ) ,
1 , 344 .
67. P .O . G oodspeed, B .L . S c o t t , and J .G . B u r r ,
J . P h y s . Chem., (1 9 6 5 ) , 1149.
68 . R. S . D av id so n and P .R , S t e i n e r , J . Chem. Soc . (C ) ,
(1 9 7 1 ) , 1682 .
69 . R .S . D a v id so n , K. H a r r i s o n , and P .R . S t e i n e r ,
I n p r e s s .
70. J . G u t t e n p la n and S .G . Cohen, Chem. Comm.,
(1 9 6 9 ) , 247.
71. S .G . Cohen, S. Orman, and D.A ̂ L a u f e r , J . Amer.
Chem. S o c . , ( 1 9 6 2 ) , gjji, 3905 .
72 . G .S . Hammond an d P .A . L e e rm a k e rs , J . Amer. Chem.
S o c . , (1 9 6 2 ) , 84 , 2 0 7 .
73. K. Y o s h ih a ra and D .R . K e a rn s , J . Chem. P h y s . ,
(1 9 6 6 ) , 4 1 , 1991 .
74. V/.E, Bachmann, J . Amer. Chem. S o c . , (1 9 3 3 ) , 55 .
3 9 1 .
75. P . Bergmann and Y. H i r s h b e r g , J . Amer, Chem. S o c . ,
(1 9 4 3 ) , 1429 .
76. See f o r exam ple \ J . N . P i t t s , J r . , R .L . L e t s i n g e r ,
R .P . T a y l o r , J .M . P a t t e r s o n , G. R e ck ten w a ld , a n d
R .B . M a r t in , J , Amer. C h em ,S o c ., (1 9 5 9 ) , 81 , 1068 .
149
77. J . M, B ru c e , Q u a r t . R e v . , (1 9 6 7 ) , 4 0 5 .
78 . J . C . Morgan and H.R. P yne , J . P h y s . Chem.,
(1 9 3 0 ) , 3 4 , 1378.
79 . C .S . F o o te , S c ie n c e , (1 9 6 8 ) , l 6 2 . 963 .
80 . P . J . Y/agner, Mol. P h o to c h em ., (1 9 6 9 ) , 1 , 71 .
81. P . J , W agner and I . K o ch ev a r , J . Amer. Chem. S o c . ,
(1 9 6 8 ) , 9 0 , 2232 .
82 . S .G . Cohen and A.D . L i t t , T e t , L e t t s . , ( 1 9 7 0 ) ,
837.
33. S .G . Cohen and H.M. Chao, J . Amer. Chem. S o c . ,
(1 9 6 8 ) , 2 0 , 165.
84 . R .S . D a v id so n , P .F . Lam beth , J . F . M cK e lla r ,
P .H , T u r n e r , and R. W ilso n , Chem. Comm., (1 9 6 9 ) , 732 .
85 . N . J . T u r ro and R. E n g e l , J . Amer. Chem. S o c . ,
(1 9 6 9 ) , 21 , 7113 .
8 6 . E.M. V o ig t and C, R e id , J . Amer, Chem, S o c . , ( 1 9 6 4 ) ,
8 6 , 3930 .
87. P .G . F a r r e l l and J . Newton, J . P h y s , Chem., (1 9 6 5 ) ,
62., 3506 .
8 8 . U n p u b l ish e d r e s u l t s - J . Wood.
89. J .M . D ereppe and M. Van M eers sc h e , B u l l , Soc . Chim.
B e ig e s , ( I 9 6 0 ) , 6 9 . 4 6 6 .
90 . R. P h i l i p p e and A.M, P i e t t e , B u l l , S o c . Chim. B e ig e s ,
(1 9 5 5 ) , 64 , 600 .
91 . T. Amano, H. K uroda , and H. Akam atu, B u l l . Chem.
Soc . J a p . , (1 9 6 8 ) , 4 1 , 83 .
92 . C .G . S chw albe , W. S c h u lz , and H. Jo c h h e im ,
B e r . , (1 9 0 8 ) , 4 1 , 3790 .
150
9 3 . Y . Uyeda and E .E , R e id , J , Amer. Chem, S o c . ,
( 1 9 2 0 ) , 2 3 8 6 .
9 4 . ^ H.D. C r o c k fo r d , and T .B . D o u g la s , J . Amer. Chem.
S o c . , (1 9 3 4 ) , 5 6 , 1 4 7 2 .
9 5 . A . I . V o g e l , ' ' P r a c t i c a l O rg a n ic C h e m i s t r y ' ' ,
Longmans, ( 3 r d . e d i t i o n ) , P . 682.
9 6 . P .D . C h a ttaw ay and K . J . P , O r to n , B e r . , (1 9 0 0 ) ,
3 3 , 2396.
9 7 . R. S to e rm e r and P . Hoffm ann, B e r . , (1 8 9 8 ) , 3 1 .
2 5 3 1 .
9 8 . G. J u s t , Z. P h y s i k . , Chem., (1 9 0 1 ) , 37 , 34 2 .
9 9 . J . H o r i u t i , S c i .P a p e r s I n s t . P h y s . Chem. R e s e a rc h ,
(T ok yo), (1 9 3 1 ), 17 , 1 2 5 .
100 . H. K l i n g e r , A n n a len , ( 19I I ) , 3 8 2 . 221.
1 0 1 . U n p u b l ish e d r e s u l t s - D. B rim age .
102. G .R. Clemo and H. M cllv /a in , J . Chem. S o c . , (1 9 3 4 ) ,
1 9 9 1 .
1 0 3 . A . I . V o g e l , ' ' P r a c t i c a l O rg a n ic C h e m i s t r y ' ' ,
Longmans, ( 3 r d . e d i t i o n ) , P . 749 .
1 0 4 . W. B ra d le y and F . V/. P e x to n , J . Chem. S o c . , (1 9 5 4 ) ,
4 4 3 6 .
1 0 5 . R .A . Ogg and F.V/. B e rg s t ro m , J . Amer. Chem. S o c . ,
(1 9 3 1 ) , 5 3 , 1846.
