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 Ti^III and Fe^II proceeds via one-electron transfer to yield SO₄ ^–· and OH^–(rather than SO₄ ^{2 –} 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).