Organic Chemistry

856 CHAPTER 20 More About Oxidation–Reduction Reactions

Because the oxygen can add from the top or the bottom of the plane containing the

double bond,trans-2-butene forms a pair of enantiomers; cis-2-butene forms a meso

compound—it and its mirror image are identical (Section 5.10).

Increasing the electron density of the double bond increases the rate of epoxidation

because it makes the double bond more nucleophilic. Alkyl substituents increase the

electron density of the double bond. Therefore, if a diene is treated with only enough

peroxyacid to react with one of the double bonds, it will be the most substituted dou-

ble bond that is epoxidized.

PROBLEM 12

What alkene would you treat with a peroxyacid in order to obtain each of the following

epoxides?

a. c.

b. d.

PROBLEM 13

Give the major product of the reaction of each of the following compounds with one equiv-

alent of a peroxyacid. Indicate the configuration of the product.

a. c.

b. d.

PROBLEM 14

Show how the following target molecules could be synthesized from propene:

a. 1-methoxy-2-propanol c. 2-butanone

b. 2-butanol

PROBLEM 15

Explain why an epoxide is a relatively stable product, whereas a bromonium ion is a reac-

tive intermediate.

CH 2 CHC CH 2

CH 3

C

H

CH 3

C

CH 3 H

CH 3

H 3 CCH 2 CH 3

H C C H

O

H 2 C CHCH 2 CH 3

O

H 2 C

H 3 CH

H C C CH 2 CH 3

O

O

+ RCOOH

O O O

+ RCOH

O

limonene

one equivalent

+

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