Original scientific paper

The Contribution of Tunneling to Secondary Isotope Effects

William H. Saunders, Jr. ; Department of Chemistry, The University of Rochester, Rochester, New York 14627, USA

Abstract

Tunneling has long been recognized as a potential contributor to rates and isotope effects in hydrogen-transfer processes, and there is by now a substantial body of experimental evidence as well. By contrast, little has been said until relatively recently about possible contributions of tunneling when the isotopically-substituted hydrogen is not transferred in the rate-determining step. Over the last ten years evidence has accumulated that tunneling by the non-transferred hydrogen attached to a carbon atom from which hydrogen is transferred is a plausible explanation of abnormal temperature dependences of isotope effects and of the non-additivity of isotope effects from multiple isotopic substitution. This paper reviews that evidence, and discusses the scope and limitations of tunneling contributions to secondary isotope effects.

Keywords

Hrčak ID:

137112

URI

https://hrcak.srce.hr/137112

Publication date:

15.10.1992.

Visits: 871 *