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Australian Journal of Chemistry Australian Journal of Chemistry Society
An international journal for chemical science
RESEARCH ARTICLE

Model Calculations of Isotope Effects. III. Isotope Effects in Hydrogen Transfer Reactions, and Transition State Force Fields

DJ McLennan

Australian Journal of Chemistry 32(9) 1869 - 1882
Published: 1979

Abstract

Model calculations of kinetic isotope effects for the reactions:

C2H6+·CH3 ·C2H5+CH4

CH4 + ·CF3 ·CH3+CHF3

are reported. Transition state geometries were those calculated by Dewar and coworkers using the MNDO semiempirical method. Transition state force fields were formulated from empirical expressions for stretching, bending, linear bending and interaction valence force constants by using bond orders as disposable parameters. Although it proved impossible to assign a best force field to either reaction, the calculated isotope effects generally were in satisfactory agreement with experiment, and were better than those calculated from the MNDO potential energy surface. Hydrogen tunnelling is apparently implicated in the CH4+ CF3 reaction.

https://doi.org/10.1071/CH9791869

© CSIRO 1979

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