The kinetics of the oxidation of quinol by aquocobalt(III) ions in aqueous perchlorate media

Abstract

The rapid reaction of Co^III, aq ions with quinol, QH₂, has been studied by use of the stopped-flow technique. Oscilloscope traces show that an intermediate Co^III–QH₂ complex is formed, and the rate of oxidation of QH₂ is of the first order in both [Co^III] and [QH₂] and independent of acidity in the range 0·2–2·0M-HClO₄ at ionic strength µ= 2·0. The overall energy of activation E= 9·7 ± 0·5 kcal. mole^–1 and the overall entropy of activation ΔS*=–14 ± 2 cal. deg.^–1 mole^–1. These are compared with E and ΔS* for the oxidation of QH₂ by Mn^III, Fe^III, and Ce^IV.