Isotope effects in nucleophilic substitution reactions. IV. The effect of changing a substituent at the α carbon on the structure of SN2 transition states

Abstract

Kinetic studies, secondary α-deuterium kinetic isotope effects, primary chlorine kinetic isotope effects (1), Hammett ρ values determined by changing the substituent in the nucleophile, and activation parameters have been used to determine the detailed (relative) structures of the transition states for the SN2 reactions between para-substituted benzyl chlorides and thiophenoxide ion. A rationale for the U-shaped Hammett ρ plots observed when para-substituted benzyl compounds react with negatively charged nucleophiles is also presented.