The Foundations of Chemistry

Organic reactions are sometimes

written in extremely abbreviated form.

This is often the case when a variety of

common oxidizing or reducing agents

will accomplish the desired conversion.

28-5 Oxidation–Reduction Reactions 1121

Formaldehyde is quite soluble in water; the gaseous compound can be dissolved in water
to give a 40% solution.
Acetaldehyde can be prepared by the similar oxidation of ethanol.

Oxidation of tertiary alcohols is difficult because the breaking of a carbon–carbon bond
is required. Such oxidations are of little use in synthesis.

Reduction of Carbonyl Compounds

Reduction of a variety of compounds that contain the carbonyl group provides synthetic
methods to produce primary and secondary alcohols. A common, very powerful reducing
agent is lithium aluminum hydride, LiAlH 4 ; other reducing agents include sodium in
alcohol and sodium borohydride, NaBH 4.

Oxidation of Alkylbenzenes

Unsubstituted aromatic hydrocarbons (Sections 27-5, 27-6) are quite resistant to oxida-
tion by chemical oxidizing agents. The reactions of strong oxidizing agents with
alkylbenzenes illustrate the stability of the benzene ring system. Heating toluene with a
basic solution of KMnO 4 results in a nearly 100% yield of benzoic acid. The ring itself
remains intact; only the nonaromatic portion of the molecule is oxidized.

carboxylic acid

reduction

RC

O

OH RCH 2 OH

ester 1 ° alcohol(s)

1 ° alcohol

aldehyde

reduction

RC

O

H RCH 2 OH 1 ° alcohol

reduction

RC

O

OR RCH 2 OH R OH

ketone 2 ° alcohol(s)

reduction

RC

O

RCH

OH

R R

Hy

drog

encontentin

cre

ase

s

2CH 3 CH 2 OH O 2 2CH 3 C 2H 2 O

O

300 °C H

Cu

ethanol acetaldehyde

2CH 3 OH O 2 2H C 2H 2 O

O

H

300 °C

Cu

methanol formaldehyde