Metal-ion catalysis in some reactions of hexacyanoferrate(III) ions. Part I. Copper catalysis in the oxidation of cysteine and related thiols

Abstract

The formation of disulphide compounds from cysteine, N-acetylcysteine, and 3-mercaptopropanoic acid, by oxidation with hexacyanoferrate(III) ions, is catalysed by small amounts of copper salts, present as impurities. The rate law for the copper-catalysed oxidation is established. The mechanism of reaction involves thiol complexes of copper(I–III) and an intermediate, thought to be the radical species RSSR^–˙, or its protonated form RSSRH˙.