Organic Chemistry

PROBLEM 30

Chloramphenicol is a broad-spectrum antibiotic that is particularly useful against typhoid

fever. What is the configuration of each asymmetric carbon in chloramphenicol?

chloramphenicol

NHCCHCl 2

HO H

H CC

O

NO 2

CH 2 OH

206 CHAPTER 5 Stereochemistry

Notice that enantiomers have the opposite configuration at both asymmetric carbons,

whereas diastereomers have the same configuration at one asymmetric carbon and the

opposite configuration at the other.

PROBLEM 29

Draw and name the four stereoisomers of 1,3-dichloro-2-butanol using:

a. perspective formulas b. Fischer projections

Tartaric acid has three stereoisomers because each of its two asymmetric carbons

has the same set of four substituents. The meso compound and the pair of enantiomers

are named as shown.

The physical properties of the three stereoisomers of tartaric acid are listed in

Table 5.1. The meso compound and either one of the enantiomers are diastereomers.

Notice that the physical properties of the enantiomers are the same, whereas the phys-

ical properties of the diastereomers are different. Also notice that the physical proper-

ties of the racemic mixture differ from the physical properties of the enantiomers.

(2R,3S)-tartaric acid

a meso compound

(2R,3R)-tartaric acid

a pair of enantiomers

a pair of enantiomers

Fischer projections of the stereoisomers of tartaric acid

(2S,3S)-tartaric acid

COOH

COOH

OH

H OH

H

COOH

COOH

OH

HO H

H

COOH

COOH

H

H OH

(^2323) HO (^23)
(2R,3S)-tartaric acid
a meso compound
HOOC
H
HO
H
OH
COOH
C C
(2R,3R)-tartaric acid
perspective formulas of the stereoisomers of tartaric acid
HOOC
H
HO
OH
H
COOH
C C
(2S,3S)-tartaric acid
H
HO
HOOC
H
COOH
OH
C C
22333 2
Tutorial:
Identification of stereoisomers
with multiple asymmetric
carbons
Table 5.1 Physical Properties of the Stereoisomers of Tartaric Acid
Melting Solubility,
point, °C at 15 °C
(2R,3R)- acid 170 139
(2S,3S)- acid 170 139
(2R,3S)-Tartaric acid 140 0 ° 125
(;)-Tartaricacid 206 0 ° 139
(-)-Tartaric -11.98°
(+)-Tartaric +11.98°
[A]^25 D°C g/100 g H 2 O