Theoretical investigation of the origin of secondary α-deuterium kinetic isotope effects

Although the secondary α-deuterium kinetic isotope effect upon the degenerate S_N2 reaction of chloromethane with chloride anion arises from changes in α-CH stretching force constants, α-substitution by methyl and/or methoxy groups shows this inverse inductive contribution to be approximately constant and reveals that the trend in the isotope effect (calculated by semiempirical molecular orbital theory) is determined by changes in bending force constants, in accord with the conventional view.