Competing elimination and substitution reactions of simple acyclic disulfides

Abstract

MP2/aug-cc-pVDZ and B3LYP/cc-pVDZ calculations of the reactions of CH₃SSR (R = H or CH₃) with fluoride, hydroxide or allyl anion in the gas-phase were performed to determine the mechanism for both elimination and substitution reactions. The elimination reactions were shown to follow the E₂ mechanism. The substitution reactions with hydroxide and fluoride proceed by the addition–elimination mechanism, but those with allyl anion proceed by the S_N2 mechanism. The elimination reactions with F⁻ and HO⁻ are preferred to the substitution reactions, while allyl anion prefers the substitution route.