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 Ti^III and organic radicals in a Ti^III–Cu^II–H₂O₂–RH reaction system suggests that one-electron transfer from Ti^III to Cu^II(k ca. 10⁶ dm³ mol^–1 s^–1) is followed by extremely rapid reaction of Cu^I with organic radicals (produced by ˙OH). For some substrates, e.g. ethanol, a chain reaction occurs involving reduction of Cu^II(by ˙CHMeOH) and oxidation of Cu^I(by ˙CH₂CH₂OH). The decomposition of S₂O₈^2– by Ti^III or Cu^II is dramatically accelerated when both metal ions are present: the rate constant for reaction between Cu^I and S₂O₈^2– is estimated as 10⁶ dm³ mol^–1s^–1.