Advices For Studying Organic Chemistry

C

H 3 C CH 3

C

H H

O O+

O

O

O

O

cis-2,3-Dimethyloxirane (b)

C

H 3 C CH 3

C

H H

H

HA

H

O

H

H 2 O

C

CH 3

H 3 C

H C

H

H

O

H

H +

C

H 3 C

CH 3

C H

H

H

O

H

+ H

C

CH 3

H 3 C

H C

H

H

HO

C

H 3 C

CH 3

C H

H

H

OH

A−

A−

(2R,3R)-2,3-Butanediol

(2S,3S)-2,3-Butanediol

(a)

Figure 11.2 Acid-catalyzed hydrolysis of cis-2,3-dimethyloxirane yields
(2R,3R)-2,3-butanediol by path (a) and (2S,3S)-2,3-butanediol by path
(b).

C

H CH 3

C

H 3 C H

O O+

O

O

O

O

C

H CH^3

C

H 3 C H

H

HA

H

O

H

H 2 O

C

CH 3

H

C

H 3 C

H

H

O

H

H +

H C

CH 3

C H

H 3 C

H

O

H

+ H

C

CH 3

H

C

H 3 C

H

H

HO

H C

CH 3

C H

H 3 C

H

OH

A−

A−

(2R,3S)-2,3-Butanediol

(2R,3S)-2,3-Butanediol

These moleculea are identical: they

both represent the meso compound

(2R,3S)-2,3-butanediol.

One trans-2,3-

dimethyloxirane

enantiomer

Figure 11.3 The acid-catalyzed hydrolysis of one trans-2,3-dimethyloxirane
enantiomer produces the meso (2R,3S)-2,3-butanediol by path (a) or
path (b). Hydrolysis of the other enantiomer (or the racemic
modification) would yield the same product.