Stabilization of oxidized sulphur centres by halide ions. Formation and properties of R2S∴X radicals in aqueous solutions

Abstract

In the presence of halide ions, stabilization of oxidized sulphur centres in organic sulphides can occur via formation of three electron S∴X bonds to yield R₂S∴X radicals. An equilibrium is found to exist between these species, X₂^–˙ radical anions, and (R₂S)₂⁺˙ radical cations. Equilibrium constants for the processes X₂^–˙+ R₂S ⇌ R₂S∴X + X^–, R₂S∴X + R₂S ⇌(R₂S)₂⁺˙+ X^–, R₂S∴X ⇌ R₂S⁺˙+ X^–, and R₂S∴X ⇌ R₂S + X˙ have been determined, together with the optical properties of R₂S∴X, where R = Me and Et, and X = Cl, Br, and I. The absolute stability of the S∴X bond increases as the difference in electronegativity between S and X decreases and is thus highest for R₂S∴I. In addition, rate constants for formation and decay processes of R₂S∴X are reported.