Reaction of the aquacopper(I) ion with hydrogen peroxide. Evidence for a CuIII(cupryl) intermediate

Oxidation of CH3OH to HCHO occurs as a chain reaction on γ-irradiation of deaerated aqueous CH3OH + H2O2+ Cu2+aq solutions. The reaction of Cu+aq with H2O2 is a propagation step. The chain-length and the dependence of HCHO formation rate on radiation dose, CH3OH concentration and pH are not compatible with a mechanism that includes production of the free hydroxyl radical, OH ˙, by the Cu+aq+ H2O2 reaction. It is suggested that an intermediate is formed by this reaction that reacts with methanol with a rate constant not greater than 4 × 105 dm3 mol–1 s–1, and the main features of the results are explained on this basis. The reactivity of the proposed intermediate is shown to be similar to that of the CuIIIaq(cupryl) species, produced by reaction of OH ˙ with Cu2+aq.