Solvent effects on nucleophilic substitution reactions. III. The effect of adding an inert salt on the structure of the SN2 transition state

Article abstract of DOI:10.1139/v96-283

The nitrogen and secondary α-hydrogen-deuterium kinetic isotope effects found for the S_N2 reaction between thiophenoxide ion and benzyldimethylphenylammonium ion at different ionic strengths in DMF at 0°C indicate that the structure of the transition state changes markedly with the ionic strength of the reaction mixture. In fact, a more reactant-like, more ionic, transition state is found at the higher ionic strength. This presumably occurs because a more ionic transition state is more stable in the more ionic solvent.