Hydroxylation. Part IV. Oxidation of some benzenoid compounds by Fenton's reagent and the ultraviolet irradiation of hydrogen peroxide

Abstract

The pH of the solution has a marked effect on the relative amounts of the various products formed by the oxidation of benzene, toluene, or anisole by Fenton's reagent; for example, as the pH is lowered, toluene gives an increased proportion of bibenzyl compared with the cresols, while benzene gives an increased proportion of phenol compared with biphenyl. At pH 2·5, both the yields and the distribution of the methoxyphenols from the oxidation of anisole are strongly dependent on the presence of oxidants other than the hydroxyl radical. The bases of these effects are discussed in the light of these and other observations, and particular attention is drawn to the importance of the one-electron oxidation of (substituted) hydroxycyclohexadienyl radicals, as compared with alternative reaction paths for these species, in determining the yield of each phenol.