kinetic isotope effect
The effect of isotopic substitution on a @[email protected] is referred to as a kinetic @[email protected] For example, in the reaction:
the effect of isotopic substitution in reactant A is expressed as the ratio of rate constants \(\frac{k^{\text{l}}}{k^{\text{h}}}\), where the superscripts \(\text{l}\) and \(\text{h}\) represent reactions in which the molecules A contain the light and heavy @[email protected], respectively. Within the framework of @[email protected] in which the reaction is rewritten as:
and with neglect of isotopic mass on @[email protected] and the @[email protected], \(\frac{k^{\text{l}}}{k^{\text{h}}}\) can be regarded as if it were the @[email protected] for an @[email protected] reaction between the @[email protected] [TS] and the @[email protected] reactant A, and calculated from their vibrational frequencies as in the case of a @[email protected] Isotope effects like the above, involving a direct or indirect comparison of the rates of reaction of @[email protected], are called '@[email protected]', in contrast to @[email protected], in which a single substrate reacts to produce a non-statistical distribution of @[email protected] product molecules.
See also:
isotope effect
PAC, 1994, 66, 1077. (Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)) on page 1130 [Terms] [Paper]