Organic Chemistry

232 CHAPTER 5 Stereochemistry

different set of stereoisomeric products. When a reactant
that does not have an asymmetric carbon forms a product
with one asymmetric carbon, the product will be a racemic
mixture.
In syn additionthe two substituents add to the same side
of the double bond; in anti additionthey add to opposite
sides of the double bond. Both syn and anti addition occur

in electrophilic addition reactions that take place by way of

a carbocation or a radical intermediate. Addition of to an

alkene is a syn addition reaction. Hydroboration–oxidation

is overall a syn addition of water. Addition of is an anti

addition reaction. An enzyme-catalyzed reaction forms

only one stereoisomer; an enzyme typically catalyzes the

reaction of only one stereoisomer.

Br 2

H 2

Key Terms

absolute configuration (p. 209)
achiral (p. 184)
amine inversion (p. 217)
anti addition (p. 222)
asymmetric carbon (p. 184)
biochemistry (p. 230)
chiral (p. 184)
chiral catalyst (p. 213)
chiral probe (p. 213)
chirality center (p. 185)
cis isomer (p. 183)
cis–trans isomers (p. 182)
chromatography (p. 213)
configuration (p. 188)
configurational isomers (p. 182)
constitutional isomers (p. 182)
dextrorotatory (p. 193)
diastereomer (p. 197)
diastereotopic hydrogens (p. 216)
enantiomer (p. 186)

enantiomerically pure (p. 195)

enantiomeric excess (ee) (p. 196)

enantiotopic hydrogens (p. 215)

enzyme (p. 213)

erythro enantiomers (p. 198)

Fischer projection (p. 187)

geometric isomers (p. 183)

isomers (p. 182)

levorotatory (p. 193)

meso compound (p. 201)

observed rotation (p. 194)

optical purity (op) (p. 195)

optically active (p. 193)

optically inactive (p. 193)

perspective formula (p. 186)

plane of symmetry (p. 201)

plane-polarized light (p. 192)

polarimeter (p. 193)

prochiral carbon (p. 216)

pro-Rhydrogen (p. 216)

pro-Shydrogen (p. 216)

racemate (p. 195)

racemic mixture (p. 195)

Rconfiguration (p. 188)

regioselective (p. 218)

relative configuration (p. 209)

resolution of a racemic mixture (p. 212)

Sconfiguration (p. 188)

specific rotation (p. 194)

stereocenter (p. 187)

stereochemistry (p. 218)

stereoisomers (p. 182)

stereoselective (p. 218)

stereospecific (p. 219)

syn addition (p. 222)

threo enantiomers (p. 198)

trans isomer (p. 183)

Problems

53. Neglecting stereoisomers, give the structures of all compounds with molecular formula Which ones can exist as
    stereoisomers?


54. Draw all possible stereoisomers for each of the following compounds. State if no stereoisomers are possible.
    a. 1-bromo-2-chlorocyclohexane g. 1,2-dimethylcyclopropane
    b. 2-bromo-4-methylpentane h. 4-bromo-2-pentene
    c. 1,2-dichlorocyclohexane i. 3,3-dimethylpentane
    d. 2-bromo-4-chloropentane j. 3-chloro-1-butene
    e. 3-heptene k. 1-bromo-2-chlorocyclobutane
    f. 1-bromo-4-chlorocyclohexane l. 1-bromo-3-chlorocyclobutane


55. Name each of the following compounds using R,Sand E,Z(Section 3.5) designations where necessary:
    a. c. e.

b. d. f.

BrCH 2 CH 2 CH 2 CH 2 CHCH 3

Br

CH 3

CH 3

CC CC

CH 3 CH CH 2 CH 2 CH 2 CH 3

H 3 C CH 2 CH 2 Cl

CH 3

CC

F I

Cl Br

Br

H

CC

F

Cl Br

CH 3

CCH 2

CH 2

CH 2 CH 3

CH 2 CH 3

H

C 5 H 10.