Free radical oxidation of organic sulphur compounds in aqueous solution

Abstract

Complexed radical cations are formed as transient products in the one-electron oxidation of organic sulphides by hydroxyl radicals. Intermolecular complexes, (R₂S ∴ SR₂)⁺, are characterized by a 3-electron bond between sulphur atoms of two different molecules, absorption maxima around 500 nm and an equilibrium (R₂S)₂⁺_.⇌ R₂S⁺_.+ R₂S. In addition, intramolecular complex formation yielding [graphic omitted] is observed in the oxidation of 1,4-di, 1,3-di, and 1,3,5-tri-thiane. In these complexes a 3-electron-through-space-bond between two sulphur atoms of the same molecule is established. Absorption maxima are red shifted to ≥600 nm. Stabilization of an oxidized sulphur atom can also be effected by hetero-atoms other than sulphur. R₂S ∴ Br(Cl) are formed in the reaction of either R₂S with Br₂[graphic omitted](Cl₂[graphic omitted]) or the oxidized sulphide with Br^–(Cl^–). Equilibrium constants for the complexes, spectral and kinetic data on the neutral radicals and radical cations are reported and discussed.