Kinetics of chlorine isotope exchange reaction between sodium chloride-36 and triphenyltin chloride in mixed solvents

Isotope exchange reaction between NaCl-36 and triphenyltin chloride in dioxane-water (8020% w/w) and ethanol-water (9010% w/w) mixed solvents has been studied at 25, 35 and 50 °C. The exchange reaction was found to proceed via a bimolecular S_N2, limiting mechanism with reaction rates depending on the solvent used. Inhibition of the exchange in ethanol-water is probably due to solvation of chloride ion through hydrogen bond formation. The rate laws for the exchange reactions are: R_e=3.24×10⁹ e^–65550/RT [Rh₃SnCl] [NaCl] in dioxanewater and R_e=6.61×10⁸ e^–69600/RT [Ph₃SnCl] [NaCl] in ethanol-water, where is the degree of dissociation of NaCl and R_e is the rate of exchange in mol l^–1 s^–1. The activation parameters H^*, S^* and G^* are reported.