Investigation of the model enzyme oxidation of phenol by peracetic acid

Abstract

The pathway of the reaction of phenol with peracetic acid to yield hexa-2,4-dienedioic acid (1) and phenoquinone (p-benzoquinone–2 phenol)(2) has been investigated by chromatographic, radiochemical, spectroscopic, and kinetic techniques. These have shown that pyrocatechol and o-benzoquinone are discrete intermediates on the route to the dicarboxylic acid (1), and hydroquinone and p-benzoquinone on the route to phenoquinone. The rate of the side reaction of o-benzoquinone with water is slow compared with that of its oxidation by peracetic acid. However, its side reaction with pyrocatechol is more rapid, leading to a reduction in the yield of hexa-2,4-dienedioic acid. The oxidation of the dihydroxybenzenes to their quinones is catalysed by copper(II) ions. It has been concluded that peracetic acid is a poor model for hydroxylating and ring-cleaving enzymes, but may provide a useful parallel for the oxidation of pyrocatechol by o-diphenol–oxygen oxidoreductase.