Reactions of hydrogen atoms with Cu2+ and Cu+ in aqueous solution
Abstract
The rate-constant ratio k(H˙+Cu2+)/k(H˙+methanol)= 34±6 was determined by measurement of the H2 yields from γ-irradiated Cu2++methanol solutions under conditions where the two solutes compete for H atoms.
The value of the ratio k(H˙+Cu+)/k(H˙+Cu2+)= 200±100 was obtained from measurement of the steady-state concentration of CuI in the γ-radiolysis of the CuII+methanol system ([H+]= 0.01–0.1 mol dm–3). The H2 and HCHO yields (for [H+]= 0.1 mol dm–3) were consistent with the assumed mechanism. An observed dependence of the H2 yield on [H+] is interpreted in terms of a competition in which the intermediate, CuH+, formed by reaction of H˙ atoms with Cu+, can react with H+ or with Cu2+.