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.