CHEM 24 Dr. Spence

1.

(s)r-\g,4./v= (R )CI

3-methylhexane

.-,K^LR)

2-methylhexane3-chloropentane

c \

qi" o

^

Draw the following compounds and indicate any stereocenters with a (*). For those that havechiral centers, draw each enantiomer and label the configuration at each stereocenter (R or S).

2-chloropentane

OH

)"-a'

(K)

For each pair of molecules below indicate whether they are identical to each other or if they are

enantiomirs of each other. For those that are identical, draw the enantiomer.

COrH OH

","$o" "T$"o,"i c) La)

! "le,ati culo,

,enc.nL= hu"(4,1, tt 1

NHr

"4;s,*Cs)

Ho*sH3?H

H-=oo

!"' ?"",cr-f cF3 F3cTcH3

H

";.4.",C S )

--tA/ .\r"/

) Determine (R) or (S) configurations at all chiral centers in the following molecules'

9"",no*

t r z \Lr\ /

ocH3

(s rCI

(s)ErtarharYq{b

Dr. Spence

Consider the molecule 1-bromo-3-chlorocyclohexane and answer the following questions: (a)how many chiral centers are present? (b) what is the maximum number of stereoisomerspossible? (c) draw all the possible stereoisomers and label them A, B, C etc. (draw them as ahexagon using wedge and dash to indicate stereochemistry). (d) define the configuration at allchiral centers and describe the relationship between all stereorsomers.

Z chr(c^\ ce"rttc), 2' . I mo x fhrrur:'1,,'rf(1

CilrottL,$"uf

f "'^tf "'trtlzoFf

fNE,D

O-(R)-hypothetical a

lcrl =-32.0 d'^7\ lc

(tr

Draw all possible stereoisomers of the following compound. To make it easier, use Fischer

Cr{1or{

flo

l{ r> ,TD,IcH

Cr{zorl CdzPrl{,n850enan f*n^t(\

Given the following information about a hypothetical molecule, calculate the Yo optical purity of

a sample containing a mixture of the two enantiomers with an optical rotation [a] of (a) +33 .9'

and @16) _�l4.Io. Foi each of these mixtures also provide the relative o/o of each enantiomer (%R

and %S).

| (+)-(S)-hypothetical

n.\ 'a [6x]:+37.6c

q#r*lvs = fia3'% e&,'l,to/" {qrvrttc ,

y- A'= &fi'75%

% 9 = c t ; ' l % S = 7 l , a 5 v b

% 4 , ' 4 , 3

CHE}i{24

= { (:

c lnY)

AJ--SC, l

:(fi)=

ciC

Itr,n Uv}itr

n "c-9 * o

?r.ol-<reoot6%

0 + 9frtQ9*tC*(7

C|"tlcil

C IO

CF\.pfl

CHEM 24 Dr. Spence

7. For each pair of molecules below indicate if they are identical, enantiomers or diastereomers.

(2R,3R,4R ,5R)-2,3,4,5-tetrachto.fii&?FofiW$,h,0*,r, )-2,3,4,S-tetrachlorohexane

evro.n\u'nrec>/\7cu.r ."\roHt t t l9ou ..*cH,

H. ,CH: HrC. .CHr\ - / \ _ . /

H : C H H H

l .

c/rc{ )lt(fbrv*6'

to[o"r\ r,al (*t2 )

crt"'"'t])4cu, Hrc*

/"\/"n t i l\-,.-

t u

1. OsOa2. NaHSO3

H Hl l

H3c-.|- Br Br--]- cHs

H3Cf Br Br--|- H

H CHst i r

drca) ftfrun^t(5

-+*o{e-,-&crlov

ff-ouI-\.J-- o.rl

1. OsOa2. NaHSO3

gnGfll"',)nEf >tr*t)'l chn6:{ I€qvc,l cn*1,*rn$

Jra2hrturrt()Vo7'v-t Ch,<al

***:, "rn'*nTb

Jiq>hrrtrnef>!7"th ch.(o'lun€r1.tal aftJbflt>

,J,olJ*'re,lrrcq5Urreq,tul a'rna{tfi

J oH BrzV /l\-.\,,'\ +

nC h'r&l

Draw all possible (stereoisomeric) products from each of the following reactions. Label theproducts A, B, C, etc and describe the relationship between the possible products. Indicatewhich molecules are chiral. Indicate if all products form in equal amounts or unequal amounts.If the product mixture is expected to be optically active check the box in front of the reaction.

/:d,, oill lI

_ - l l r l6 f l

r+

,I--{,,, od/ - [ , , , e i1

l1

CIl-{ wryR 9r-

tt.+;z:-( t t\-5--;

7

rt

tneS7; vlot Cht(a l

'Lt''*'r W'HBr

{nv,J

CHEM 24 Dr. Spence

9. While considering the cyclohexane ring as a planar hexagon, draw an optically active version of1,2,3,4,5,6-hexachlorocyclohexane.

Cl r l t / /

, r , , , C i

CI$tt o*Lo h*ot c^

{la*rnt CIC 51nn'r'et*7il

C I

10. For the first compound in question 8, identifu all pro-chiral sp'carbons. Are you looking at theRe face or Si face? For the last compound in question 8, identify all pro-R positions.

/----t gro'-ch'c'""1 ((t fr*tt)

r \\- gro -ch,{a I (9, h"e)

c a nQt'' *t l t\ r ;

CH."'\t>ll l \

c>HfY'f,^u R 'l*- ftt R

11. Circle the chiral centers in the following compounds.

12. Label with a "*" all the chiral centers in the following molecules.

13. Identify the following pairs of compounds as enantiomers, diastereomers, or the same.

HO

OH

O

HO

O

OH

Cholesterol Prostaglandin E2

C

N

OCH3

O

H

H

OCH3

O

cocaine

NHCO2CH3

O

H

H3CSSS H OR

C C

C

calecheamicin

**

*

**

*

Br Br

Br Br

OHOH

OH

HO

diastereomers enantiomers

diastereomersenantiomers

14. Identify the following pairs of compounds as enantiomers, diastereomers, constitutional isomers, or the same. a. diastereomers

b. enantiomers

15. Identify the stereocenters in the following molecules and indicate whether they are R or S.

16. Using the tests for chirality we have learned, determine whether the following molecules are chiral. Determine the configuration (R or S) of any chiral centers in the molecules.

Br Br Br Br

OH

HO

HOH

H

ClHO OH

O

NH2

RS

S

not a stereocenter!

R S

S

OH

O

CH3 OHOHHO

CH3

NH2CH3 OH

Br

chiral

achiralno stereocenter

achiralmeso

achiralmeso

chiral chiral

R

S

R RS S

S

R

17. Circle those molecules below that are chiral.

18. Name the compound below. Be sure to include R,S designations.

S-3-methylhexane 19. Determine the relationship between the following pairs of molecules: enantiomers, diastereomers, identical, or structural (constitutional) isomers. a. structural isomers

b. diastereomers

c. identical -- no chiral center

Cl

Cl ClHO

Cl

Cl

OH

O CH3

CH3

CH3

Br Br

NH2

NH2

NH2

NH2

OH

HO

d. enantiomers

e. identical -- draw flat and see -- compound is meso

f. identical -- meso

OH OH

Br

OH OH

Br

CH3

CH3

CH3

H3C

OH OH OH OH