Electron spin resonance studies of the effect of copper(<scp>II</scp>) and copper(<scp>I</scp>) on the generation and reactions of organic radicals formed from the fenton reaction and the TiIII–H2O2and TiIII–S2O82–redox couples

Kinetic analysis of the intensity of steady-state e.s.r. signals from TiIII and organic radicals in a TiIII–CuII–H2O2–RH reaction system suggests that one-electron transfer from TiIII to CuII(k ca. 106 dm3 mol–1 s–1) is followed by extremely rapid reaction of CuI with organic radicals (produced by ˙OH). For some substrates, e.g. ethanol, a chain reaction occurs involving reduction of CuII(by ˙CHMeOH) and oxidation of CuI(by ˙CH2CH2OH). The decomposition of S2O82– by TiIII or CuII is dramatically accelerated when both metal ions are present: the rate constant for reaction between CuI and S2O82– is estimated as 106 dm3 mol–1s–1.