Hydrazobenzene conversion into benzidine

Hydrazobenzene, 628, 629, 632 conversion into benzidine, 633 Hydrazo compounds, 1074 table of, 1085 ... 

The conversion of a hydrazobenzene into a diaminodiphenyl upon treatment with acid is termed the benzidine rearrangement. The following mechanism for the formation of benzidine from hydrazobenzene appears reasonable ... 

The conversion of hydrazobenzene into the isomeric benzidine— discovered by the Russian chemist Zinin in the year 1846—is started catalyticaUy by mineral acids and results from the tendency of the molecule to pass into a form possessing less energy, i.e. into a more saturated condition. The reaction is suitably classified with those of which the chief characteristic is that a substituent united to nitrogen exchanges its point of attachment with an H-atom of the nucleus— usually an H-atom in the p-position. To this class belong the conversion of phenylsulphaminic acid into sulphanilic acid (p. 198), of phenyl-hydroxylamine into p-aminophenol (p. 176), and also of acetanilide into p-aminoacetophenone and of N-chloroacetanilide into p-chloro-acetanilide ... 

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