Mechanisms of peroxide decomposition. An ESR study of the reactions of the peroxomonosulphate anion (HOOSO3–) with TiIII, FeII, and α-oxygen-substituted radicals

Abstract

It is shown that decomposition of the peroxymonosulphate anion (HOOSO3–) in aqueous solution with the low-valence metal ions TiIII and FeII proceeds via one-electron transfer to yield SO4–· and OH–(rather than SO42– and ˙OH), with rate constants in the range 102– 105 dm3 mol–1 s–1. A variety of subsequent reactions of SO4–· with added substrates has been demonstrated.ESR results also reveal the efficacy of HOOSO3– as an oxidant for carbon-centred radicals generated in situ. In addition to the occurrence of rapid one-electron oxidation of alkyl radicals (e.g. Et˙, with k 3.8 × 105 dm3 mol–1 s–1) it is also established that certain oxygen-conjugated radicals undergo a novel oxidation reaction involving oxygen-transfer and subsequent fragmentation (˙CHMeOH gives Me˙, with k1.1 × 106 dm3 mol –1s–1).