Kinetics of the oxidation of quinol by aquomanganese(III) ions in aqueous perchlorate media

Abstract

The rapid reaction of aquomanganese(III) ions with quinol has been investigated in aqueous perchlorate media by use of the stopped-flow technique. The oscilloscope traces suggest the presence of an intermediate Mn^III–quinol complex. The rate of oxidation of the quinol is of the first order in [Mn^III]_Total and of the first order in [QH₂](QH₂= quinol), and the second-order rate constant increases with decreasing acidity. The manner in which this rate constant varies with acidity shows that the rate-determining step in the oxidation is an electron transfer within a complex MnQH²⁺_aq. The mechanism of the oxidation of quinol by Mn^III_aq is compared with both inner- and outer-sphere oxidations of other ligands by Mn^III_aq.