A semiempirical study of 2,2′-dichlorodiethyl sulfide SN2 and neighboring group hydrolysis reaction mechanisms in the gas phase and in aqueous solution

A PM3 and SM3-PM3 semiempirical molecular orbital study of the 2,2′-dichlorodiethyl sulfide conventional S_N2 and neighboring group hydrolysis reaction mechanisms in the gas phase and in aqueous solution is described. The calculations predict substantially faster reactions in aqueous solution, with the neighboring group mechanism always being preferred. Detailed consideration is given to the geometries, relative energies, and partial atomic charges of all species involved in the reaction mechanisms considered and the extent to which aqueous solvation impacts these quantities. The results are consistent with expectation and with reported calculations concerning the intramolecular S_N2 reaction of 2-chloroethyl methyl sulfide. We also present the lowest energy mustard chlorohydrin structures according to PM3 and AM1 conformational analysis.