Monocarboxylic Acids of the Benzene Series

This chapter reviews the monocarboxylic acids of the benzene series under two categories: those derived from benzene and its homologs and derivatives by replacing a hydrogen atom of the nucleus by the carboxyl group, that is true arenecarboxylic acids, such as benzoic acid, toluic acid, and so on, and those formed by the replacement of a hydrogen atom of the side-chain (arylalkanoic acids, for example, phenylacetic acid). The aromatic carboxylic acids afford functional derivatives corresponding to those of the fatty acids. In the following, the different classes of functional derivatives are described, those of benzoic acid being taken as typical. These comprise of: esters, aroyl halides and mixed anhydrides with inorganic acids, acid anhydrides, aroyl peroxides and peracids, thio- and dithio-carboxylic acids and their derivatives, aromatic amides, benzoyl derivatives of amino acids, aroyl hydrazines, aroyl azides, arenecarbonitriles, aryl cyanides, halogenated amides, imines and so on, thioamides and thioimidates, amidines, amidrazones, hydroxamic (hydroximic) acids and hydroximoyl halides, nitrolic and nitrosolic acids, nitrile oxides, ortho-acid derivatives. Methods for the synthesis of aryl-substituted derivatives of saturated fatty acids or arylalkanoic acids include the oxidation of aralkyl alcohols and aldehydes or the hydrogenation of corresponding unsaturated acids.