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 Cu^I in the γ-radiolysis of the Cu^II+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⁺.