Organic Chemistry

88 Preparation

1. from alkenes

R-CH=CHR + KMnO4 + OH- + Heat----> 2RCOOH

2. from ROH

RCH2OH + OXIDIZING AGENT ----> RCOOH

Aliphatic carboxylic acids are formed from primary alcohols or aldehydes by reflux with
potassium dichromate (VI) acidified with sulphuric acid.

3. from toluene etc.

toluene + KMnO4 ----> benzoic acid

Alkyl benzenes (methyl benzene, ethyl benzene, etc) react with potassium manganate (VII)
to form benzoic acid. All alkyl benzenes give the same product, because all but one alkyl
carbon is lost.

No acidification is needed. The reaction is refluxed and generates KOH. The benzoic acid
is worked up by adding a proton source (such as HCl).

4. from methyl ketones

RCOCH3 + NaOH + I-I ----> RCOO- + CHI3

5. from Grignard reagents

RMgX + O=C=O ----> RCOOMgX

RCOOMgX + HOH ----> RCOOH + MgX(OH)