A COMPARATIVE MECHANISTIC STUDY OF THE OXIDATION OF PHENOLS IN AQUEOUS-SOLUTION BY OXOMANGANESE(IV) AND OXOIRON(IV) 5,10,15,20-TETRAKIS(2-N-METHYLPYRIDYL)PORPHYRIN

The kinetics of the reactions of phenol and six substituted phenols wi th oxomanganese(IV) tetra(2-N-methylpyridyl)porphyrin in aqueous solut ion (pH 7.7) have been studied. The reactions are shown to be first or der in both phenol and the oxomanganese(IV) species. The second order rate constants have been measured and the influence of the substituent s on these values have been analyzed using Hammett and modified Hammet t equations. The magnitude of the rho values obtained and the good cor relation of the data with sigma(.) and the dual parameter sigma(.) + s igma(+) suggest that, like the reactions of the analogous oxoiron(IV) tetra(2-N-methylpyridyl)porphyrin, the rate-determining step in these oxidations involves hydrogen atom abstraction from the phenol by the o xomanganese(IV) species in which the transition state has partial char ge separation.