The theory of kinetic hydrogen isotope effects

Abstract

Some of the most definite information about the part played by the tunnel effect in chemical and physical processes has come from the study of kinetic isotope effects, the theory of which is given in some detail in this chapter. The emphasis is on the comparison between the three hydrogen isotopes H, D and T, though much of the treatment has more general application. The replacement of one isotope by another can affect both equilibria and kinetics: the latter effects are by far the greater and are the only ones relevant to the tunnel effect. Kinetic isotope effects can be classified as primary, secondary and solvent effects, according to whether they involve isotopic substitution in a bond which is made or broken during reaction, in some other part of the reacting species, or in the solvent. Only primary effects are considered in this chapter. The subject is treated more extensively in a number of books and articles [112–118].