SECONDARY KINETIC ISOTOPE EFFECTS IN BIMOLECULAR NUCLEOPHILIC SUBSTITUTIONS: I. DEUTERIUM EFFECTS IN THE BUNTE SALT REACTION

The secondary deuterium isotope effects have been measured for the reaction between sodium thiosulphate and α-deuterated methyl, ethyl, and n-propyl bromide, and also for β- and γ-deuterated n-propyl bromide, in aqueous ethanol solvent. The α-deuterium isotopic rate ratios (kH/kD) are all greater than unity. These unexpected results are discussed with respect to the suggested use of the α-deuterium isotope effect as a test of mechanism in nucleophilic substitutions.