Mechanism for the Reactions of Sulfides with Hypochlorous Acid and N‐chlorosulfon‐amides: Formation of Solvated Chlorosulfonium Cation and Λ4‐sulfane Intermediates

DFT computations have been performed to study the mechanism of the reactions of sulfides with hypochlorous acid and N-chlorosulfonamides. Sulfides can attack HOCl both at chlorine and oxygen atoms. The attack at chlorine results in the formation of chlorosulfonium cation (R2SCl+) and OH- intermediates, which transform to sulfoxide product. The high free energy of activation (Delta G(double dagger)), which is needed for the formation of ionic intermediates, is decreased considerably by solvation in protic solvents. Since the attack of sulfides at the oxygen atom of HOCl has low Delta G(double dagger) value, the chlorination of sulfides can compete with the attack at the oxygen atom only in protic solvents. Kinetic studies showed that the reactivity of species, formed from N-chlorosulfonamides in protic solvents, increases in the course: RSO2NCl- << RSO2NHCl < < RSO2NCl2. The chlorination of sulfides with RSO2NHCl or RSO2NCl2 results in the formation of R2SCl+ and RSO2NH- or RSO2NCl- intermediates, respectively, and the computed and experimentally derived Delta G(double dagger) data agree in these cases. Sulfilimine (R2SNSO2R) and sulfoxide products are formed in the reaction of R2SCl+ with RSO2NH- and water, respectively. Acyloxy-chloro-lambda(4)-sulfane intermediates are produced in the reactions of N-chlorosulfonamides and sulfides, bearing 2-carboxy-phenyl group, without the intermediacy of chlorosulfonium cations. Explicit water molecules must also be included in computations for reactions proceeding with formation or destruction of ions, to get Delta G(double dagger) values, comparable with experimental data. Supporting information may be found in the online version of this paper.