THEORETICAL INVESTIGATION OF THE ORIGIN OF SECONDARY ALPHA-DEUTERIUM KINETIC ISOTOPE EFFECTS

Although the secondary alpha-deuterium kinetic isotope effect upon the degenerate S(N)2 reaction of chloromethane with chloride anion arises from changes in alpha-CH stretching force constants, alpha-substitution by methyl and/or methoxygroups 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.