Oxidative fragmentation of phenylacetic acid and related compounds induced by some oxygen-containing radicals

Abstract

The neutral and phenolic products from the oxidation of phenylacetic acid, phenoxyacetic acid, hydrocinnamic acid, and some related compounds with the titanium(III)–hydrogen peroxide system and the titanium(III)–potassium persulphate system have been determined. Their nature, and their dependence on pH, complement earlier e.s.r. evidence that the hydroxyl radical and the sulphate radical-anion react by addition to the aromatic ring to give intermediates which undergo fragmentation to an alkyl radical, carbon dioxide, and hydroxide or sulphate ion. The fragmentation of the hydroxyl-adducts is acid-catalysed. The alkyl radical can dimerise or, in some cases, undergo one-electron oxidation.

Evidence has also been obtained from product studies that adducts of phenylacetic acid or toluene with the benzoyloxy-radical, from the photolysis of dibenzoyl peroxide, undergo acid-catalysed fragmentation to give the benzyl radical.