An investigation of the nature of p-azophenol

Abstract

The isomerism of p-azophenol was first studied in detail by R. Willstätter and M. Benz (Ber. 1906, 39, 3492; 1907, 40, 1578). They found that azophenol obtained directly by the alkali fusion of p-nitrophenol differed from that obtained by the reduction of benzoquinoneazine, which is itself the oxidation product of p-azophenol. The object of their work was to discover the nature of this isomerism. A careful survey of their results led them to classify these isomers as geometric isomers.