Kinetics of oxidation of hydrogen peroxide by aquocobalt(III) ions in aqueous perchlorate media

Abstract

The rapid oxidation of hydrogen peroxide by Co^III has been investigated with initial [Co^III]∼6 × 10^–4 M using stopped-flow spectrophotometry. The oscilloscope traces and the kinetics show that two intermediate complexes related by a protonation equilibrium are involved, and the decomposition of Co^IIIHO^–₂ dominates over that of Co^IIIH₂O₂. Heats and entropies of formation of the complexes and energies and entropies of activation for their decompositions are calculated : these differ markedly from similar quantities derived from conventional experiments with [Co^III]≲7 × 10^–5 M, and this is discussed in terms of Co^III dimers.