Density functional theory gas- and solution-phase study of nucleophilic substitution at di- and trisulfides

Density functional calculations indicate that nucleophilic substitution in the thiolate-disulfide and thiolate-trisulfide exchange reactions proceeds by an addition-elimination pathway. Solution calculations were performed using B3LYP/6-31 + G* and the polarized continuum method. These solution-phase calculations indicate that for the reactions where the sulfur under attack bears a hydrogen atom, the substitution proceeds via an addition-elimination mechanism; however, when a methyl group is attached to the sulfur under attack, the S(N)2 mechanism is predicted.