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 (80:20% w/w) and ethanol-water (90:10% w/w) mixed solvents has been studied at 25, 35 and 50-degrees-C. The exchange reaction was found to proceed via a bimolecular S(N)2, 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 x 10(9) e-65550/RT [Ph3SnCl] alpha [NaCl] in dioxane-water and R(e) = 6.61 x 10(8) e-69600/RT [Ph3SnCl] alpha [NaCl] in ethanol-water, where alpha is the degree of dissociation of NaCl and R(e) is the rate of exchange in mol l-1 s-1. The activation parameters DELTA-H*, DELTA-S* and DELTA-G* are reported.