Isotope Effects in Deuterium Oxide Solution. Part II. Reaction Rates in Acid, Alkaline and Neutral Solution, Involving only Secondary Solvent Effects

The treatment previously used for estimating solvent deuterium oxide effects on acid--base equilibria is applied to kinetic secondary isotope effects on reactions which do not involve a primary deuterium isotope effect. Explanations are provided for the differing solvent isotope effects upon A-1 and A-2 reactions, for the greater nucleophilic power of OD/sup -/ over OH/sup -/, and for solvent-isotope effects in solvolyses. The calculated isotope effects, necessarily based upon approximate models for reasonable transition state structures, generally bracket the observed isotope effects. However, when the mechanistic situation is complicated, unambiguous distinction of mechanism based upon isotope effects is not possible.