Mechanism of the reaction of dialkyl sulphides with bromamine T in alkaline medium

Abstract

Bromamine T (p-MeC6H4SO2NBr–K+) reacts readily with dialkyl sulphides (R2S) to yield suiphoxides (R2SO) and sulphimides (R2SNTs). The kinetics of the reaction were investigated in buffered alkaline water-methanol solutions. In rate-determining steps HOBr and p-MeC6H4SO2NHBr formed in equilibrium reactions convert dialkyl sulphides into bromosulphonium (R2SBr+) intermediates (ρ*–1.22 and –1.11, ρI–13.3 and –14.4, respectively). Electrophilic additions of Br+ to sulphur atom are significantly hindered by the steric effect of S-alkyl groups (δ 0.713 and 0.765, ρs 0.766 and 0.792, respectively). Products are rapidly formed from bromosulphonium ions by nucleophilic displacement with OH– and p-MeC6H4SO2NH– nucleophiles. Product distribution depends on pH and the concentration of p-MeC6H4SO2NH2 but is not influenced markedly by S-alkyl groups in sulphides. Results are compared with those obtained earlier for chloramine T.