Electron spin resonance studies of the effect of copper(II) and copper(I) on the generation and reactions of organic radicals formed from the fenton reaction and the TiIII–H2O2 and TiIII–S2O82– redox couples
Abstract
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.