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mines
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Reference: Organic Chemistry, Seventh Edit ion, Francis A. Carey, 2008, McGraw Hill
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Primar Alk lamines
(R(RNNHH : one carbon directl attached to: one carbon directl attached to NN))
CHCH33CHCH22NHNH22 ethylethylamineamine
NHNH22 cyclohexylcyclohexylamineamine
CHCH33CHCHCHCH22CHCH22CHCH33 11--methylbutylmethylbutylamineamine
222
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Primary Arylamines (ArNH )
ame as ervatves o an ne.
22
NHNH22FF BrBr CHCH22CHCH33
pp--fluorofluoroanilineaniline oo
44--fluorofluoroanilineaniline
55--bromobromo--22--ethylethylanilineaniline
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Amino Grou s as Substituents
Amino rou s rank below OH rou sand higher oxidation states of carbon.
substituent.
OO
NHNH22HCHCHOCHHOCH22CHCH22NHNH22
--aminoaminobenzaldeh debenzaldeh de22--aminoaminoethanolethanol
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Secondary and Tertiary Amines
CHCH33NNHCHHCH22CHCH33 NN--methylethylmethylethylamineamine
NNHCHHCH22CHCH33
4--chlorochloro--NN--eth leth l--33--nitronitroanilineaniline
NONO22
ClCl CHCH33
CHCH33NN
--5
,,
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Ammonium Salts
A nitro en with fou substituents is ositivelcharged and is named as a derivative of
+
CHCH33NNHH33++
ClCl
NN
33++
CFCF COCO
HH
methylmethylammoniumammonium NN--ethylethyl--NN--methylcyclopentylmethylcyclopentylammoniumammonium
6chloridechloride trifluoroacetatetrifluoroacetate
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Ammonium Salts
When all four atoms attached to N are carbon,t e on s ca e a qua ernary ammon um on an
salts that contain it are called quaternaryammonium salts.
CHCH33
CHCH22 NN CHCH33 II
CHCH33
7benzyltrimethylbenzyltrimethylammoniumammoniumiodideiodide
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Physical Properties
CHCH33CHCH22NNHCHHCH33CHCH33CHCH22CHCH22NNHH22 (CH(CH33))33NN
boilingboiling
point:point:
5050 CC 3434 CC 33 CC
Boiling points of isomeric amines decrease in
going fromprimary to secondary to tertiary amines.
of being involved in intermolecular hydrogen bonding.
Secondary amines have one.
8Tertiary amines cannot be involved in intermolecularhydrogen bonds.
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Basicit of Amines
It is more useful to describe the basicity of amines
in terms of the K s of their con u ate acids thanas basicity constants Kb.
The more basic the amine, the weakeritsconjugate acid.
The more basic the amine, the largerthe pK of itsconjugate acid.
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Citing amine basicity according to the pKa of the
-reactions of amines according to the usual Brnsted.
Amines are converted to ammonium ions by acetic acid.
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Adding sodium hydroxide to an ammonium saltcoverts it to the free amine.
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Effect of Structure on Basicity
(1)(1)AlkylaminesAlkylamines areare slightly strongerslightly stronger bases thanbases thanammona.ammona.
. a
NH NH + .
CH3CH2NH2 CH3CH2NH3+ 10.8
++ ++33 22 33 44
therefore,therefore, CHCH33CHCH22NHNH22 is a stronger baseis a stronger base
12
33..
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Effect of Structure on Basicity
(2)(2)ArylaminesArylamines areare much weakermuch weaker bases thanbases thanammonia.ammonia.
. a
+
CH3CH2NH2 CH3CH2NH3+ 10.8
(CH3CH
2)2NH (CH
3CH
2)2NH
2
+ 11.1
(CH3CH2)3N (CH3CH2)3NH+ 10.8
13C6H5NH2 C6H5NH3+
4.6
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Decreased Basicity of Arylamines
by delocalization into the system of the aromatic ring.
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Decreased Basicity of Arylamines
diphenylamine a weaker base than aniline,an rp enyamne a wea er ase andiphenylamine.
CC66HH55NNHH22 (C(C66HH55))22NNHH (C(C66HH55))33NN
ppKKaa
of conjugate acid:of conjugate acid:
4.64.6 0.80.8 --55
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Effect of Substituents on
as c y o ry am nes
y groups on t e rng ncrease as c ty, u
only slightly (less than 1 pK unit).
XX NNHH22
aa
HH 4.64.6
16
..
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Effect of Substituents on
as c y o ry am nes
,
and/or para to amine group, decrease basicityan can ave a arge e ec .
XX NNHH22
XX KK of conu ate acidof conu ate acidHH 4.64.6CFCF 3.53.5
17OO22NN 1.01.0
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p-Nitroaniline
OO
OO
NHNH22NN NN NHNH22
OO OO
Lone air on amine nitro en is conu atedwith p-nitro groupmore delocalized than
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Heterocyclic Amines
Wh ?19
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The nitrogen lone pai occupies an sp3-hybridizedorbital in i eridine verus an s 2-h bridized onein pyridine.
Electrons in orbitals with more s characterare
y wcharacter.
Thus, nitro en holds on to its unshared airmore strongly in pyridine than in piperidine and
20
.
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Alkylation of Ammonia
Desired reaction is:Desired reaction is:
22 NNHH33 ++ RRXX RRNNHH22 ++ NNHH44XX
via:via:
HH33NN
RR XX HH33NN RR++
XX++ ++
then:then:HH HH
HH33NN ++ HH NN RR++
HH33NN HH ++ NN RR
21HH HH
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Alkylation of Ammonia
''
, ,, ,
and tertiary amines, plus the quaternary salt.and tertiary amines, plus the quaternary salt.
RXRX RXRX
RXRX
RR NNRXRX++
XX
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Exam le
NNHH3333 22 66 22 33 22 66 22 22
45%45%
++
CHCH33(CH(CH22))66CHCH22NNHCHHCH22(CH(CH22))66CHCH33
(43%)(43%)
s oc yamne s orme , compe es wammonia for the remaining 1-bromooctane.
23
eac on o oc yamne w - romooc ane
gives N,N-dioctylamine.
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Pre aration of Amines b Reduction
-
be reduced to an amine, including:azides
nitro-substituted benzene derivatives
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Synthesis of Amines via Azides
SN2 reaction, followed by reduction, gives a.
CHCH22CHCH22BrBr CHCH22CHCH22NN33aa 33
Azides may also be..
2. H2. H22OO
hydrogenation.
CHCH22CHCH22NNHH22
25(89%)(89%)
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Synthesis of Amines via Nitriles
SN2 reaction, followed by reduction, gives a.
CHCH33CHCH22CHCH22CHCH22BrBraa
CHCH33CHCH22CHCH22CHCH22CNCN
Nitriles may also be
HH22 (100 atm), Ni(100 atm), Ni
aluminum hydride.
CHCH33CHCH22CHCH22CHCH22CHCH22NHNH22
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Synthesis of Amines via Nitroarenes
ClCl NONO22Nitro rou s ma also
(88(88--95%)95%)
be reduced with tin (Sn)
1. Fe1. Fe HClHCl
hydrogenation.
2.2. NaOHNaOH
ClCl NHNH22
27(95%)(95%)
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S nthesis of Amines via Amides
OO OO
COHCOH
1. SOCl1. SOCl22
CCNN(CH(CH33))22(86(86--89%)89%)
.. 33 22
1. LiAlH1. LiAlH44
4appropriate reducing
2. H2. H22OOagen or s reac on.
CHCH22NN(CH(CH33))22
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Synthesis of Amines via
is subjected tois subjected to catalytic hydrogenationcatalytic hydrogenation in thein the
..
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M h i f
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Mechanism of
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Ammonia Gives a
r mary m ne
OO ++ NNHH33
HHHH22, Ni, Ni
(80%)(80%)22
Synthesis ofamphetamine () (a central nervous system stimulant)
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Primary Amines Give Secondary Amines
++
HH22, Ni, Ni ethanolethanol
CHCH CHCH CHCH NNHH
(65%)(65%)
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Secondary Amines Give Tertiary Amines
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Synthesis ofynthesis ofUsing Reductive Amination!
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