A kinetic study of the early steps in the oxidation of chlorophenols by hydrogen peroxide catalyzed by a water-soluble iron(III) porphyrin

The kinetics and mechanism of the initial steps in the oxidation of 2,4,6-trichlorophenol by hydrogen peroxide using iron(III) meso-tetra(4-sulfonatophenyl) porphine chloride as a catalyst were studied in this work. The first oxidation step is the formation of a substituted 1,4-benzoquinone. This step was also studied using a selection of differently substituted chlorophenols. It was shown that the rate constants characteristic for the oxidation of the substrate do not follow the pattern of pK(a)s, but correlate well with the C-13 chemical shifts of the carbon atoms directly bonded to the oxygen in chlorophenols. The kinetics of the catalyzed and uncatalyzed oxidation of 2,6-dichloro-1,4-benzoquinone by hydrogen peroxide was also studied. The catalyzed and uncatalyzed pathways give different products.