From alkylbenzenes
Aromatic carboxylic acids can be prepared by vigorous oxidation of
alkyl benzenes with chromic acid or acidic or alkaline potassium
permanganate The entire side chain is oxidised to the carboxyl group
irrespective of length of the side chain Primary and secondary alkyl
groups are oxidised in this manner while tertiary group is not affected Suitably substituted alkenes are also oxidised to carboxylic acids
with these oxidising reagents