The oxidation of catechol and 1:2:4-trihydroxybenzene by polyphenol oxidase

Abstract

A study of the enzymic oxidation of catechol in the presence of aniline shows that the amt. of dianilo-o-quinone produced diminishes as introduction of aniline into the oxidising catechol is delayed. The total oxygen absorbed, however, remains constant at 3 atoms per molecule of catechol. Oxidation of 1,2,4-trihydroxybenzene to hydroxyquinone is catalysed by polyphenol oxidase and in the presence of aniline 2 atom equivalents of O2 are absorbed; autoxidation requires 4 atoms. In both cases a hydroxymonoaniloquinone M.P. 210[degree] (decomp.) is isolated, no trace of dianilo-o-quinone being formed. Results indicate that the oxidation of catechol does not proceed to hydroxyquinone but to o-quinone which, in the absence of aniline, decomposes to brown material.