TRACE-METAL ION CATALYSIS - KINETICS AND MECHANISM OF OXIDATION OF METOL BY HYDROGEN-PEROXIDE IN THE PRESENCE OF IRON(III) SULFATE IN ACID PERCHLORATE

The kinetics of oxidation of N-methyl-p-aminophenol (metol) by H2O2 in the presence of trace levels of Fe-III have been studied in an HClO4 medium. The reaction mechanism is complex and the catalytic role of Fe -III in the sulphate form is indicated. The following rate law account s for the experimental observations: -d[H2O2]/dt = ](k(1)+k(2)[metol]) /1+K-1[metol]+K1K2[metol][H2O2] where k(un)(i) is the initial rate for the uncatalysed reaction. The equilibrium constants K-1 and K-2 are t he formation constants for the complexes [Fe(metol)](3+) and [Fe(metol )(H2O2)](3+), respectively. The catalytic role of Fe-III is explained by considering a ternary complex in the transition state.