Abstract
The oxidation of aniline and substituted anilines by sodium hypochlorite was studied in buffer solutions at 5°C when sodium hypochlorite was added to an excess of aniline suspended in alkaline buffer, azobenzene, 4-anilinoazobenzene, azophenine (2,5-dianilinobenzoquinonedianil), p-hydroxyazobenzene, indoaniline, a black material, possibly aniline black and a rose-red compound, possibly phenosafranone, were formed, When aniline was added to an excess of sodium hypochlorite, azobenzene, azophenine, 4-anilinoazobenzene, 2,5-dianilinobenzoquinone imide anil, and 4-aminodiphenylamine were obtained. The structure of these compounds were determined by spectroscopy and mass-spectroscopy and confirmed by comparison with authentic specimens. The nature of the products obtained is consonant with hydrazobenzene, 4-aminophenol and 4-aminodiphenyl amine being the initially formed compounds. p-Chloroaniline under similar conditions yielded tetra-p-chloroazophenine, 4,4'-dichloroazobenzene, asymmetrical azo-compounds, and blue-violet products. 2,4-Dichioroaniline and 2,4,6-trichloroaniline gave the corresponding azo-compounds, o-p- and m Nitroaniline similarly produced azo-compounds except for o-nitroaniline which was oxidised to benzofurazanoxide at pH 10 but to the azo-compound at pH 8. 2,4-Dinitroaniline yielded an azo-compound but 2,4,6-trinitroaniline failed to react. Mesidine (2,4,6-trimethylaniline) and p-aminobenzoic acid were oxidised to azo-compounds in high yields; the latter also gave appreciable amount of 2,4,6,2',4',6-hexachloroazobenzene. The hypochlorite oxidation of hydrazobenzene and nitroso-benzene gave high yields of azobenzene and nitrobenzene respectively; the oxidation of phenylhydroxylamine gave azobenzene, 4-anilino-azobenzene and other products. Acetanilide was oxidised but failed to yield any of the products obtained from aniline, the alkaline decomposition of N-chloroacetanilide follows a similar path. These reactions are compared with those of other oxidising agents and their possible mechanism are discussed. It is shown that routes involving the formation and reaction of phenylnitrenium ions (PhNH) or phenylnitrenes (PhN) are possible; the intervention of phenylamine radical (PhNH-) appears less likely.