Organic Chemistry

Introduction 843

If water is added to an alkene, the product has one more bond than the reac-

tant, but it also has one more bond. In this reaction, one carbon is reduced and

another is oxidized. The two processes cancel each other as far as the overall molecule

is concerned, so the overall reaction is neither an oxidation nor a reduction.

Oxidation–reduction reactions that take place on nitrogen or sulfur show similar

structural changes. The number of or bonds increases in reduction reac-

tions, and the number of or bonds increases in oxidation reactions. In

the following reactions, nitrobenzene and the disulfide are being reduced

(Sections 16.2 and 23.7), and the thiol is being oxidized to a sulfonic acid:

Many oxidizing reagents and many reducing reagents are available to organic

chemists. This chapter highlights only a small fraction of the available reagents. The

ones selected are some of the more common reagents that illustrate the types of trans-

formations caused by oxidation and reduction.

PROBLEM 1

Indicate whether each of the following reactions is an oxidation reaction, a reduction

reaction, or neither:

a. H^2

partially

deactivated

Pd

C

CH 3 Cl

O

C

CH 3 H

O

CH 3 CH 2 S2 CHSCH 2 CH 3 3 CH 2 SH

a disulfide a thiol

CH 3 CH 2 SH

a thiol

CH 3 CH 2 SO 3 H

a sulfonic acid

nitrobenzene

NO 2

H 2

Pd/C

HCl

Zn

HNO 3

NH 2

N¬O S¬O

N¬H S¬H

RCH CHR RCH 2 CHR

H+

H 2 O

OH

C¬O

C¬H

OH

RCH CHR RCHCHR

an alkene

Br 2

H 2 CrO 4

H 2 CrO 4

an aldehyde

RCHR

OH

an alcohol

BrBr

C

RH

O

C

R

O

C

RR

O

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