From rate constants to potential energy hypersurfaces through the transition state theory formalism. Evaluation of the activation barriers of some hydrogen abstraction reactions

A procedure for extracting various properties of potential energy hypersurfaces, such as the activation barrier Delta /b E//sup ne / and the imaginary frequency nu /sub Im//sup ne / from experimental rate constants, is described using the formalism of the transition state theory including an Eckart tunnelling correction. The procedure is applied to three hydrogen transfer reactions. It is found that reliable activation barriers can be obtained provided that accurate experimental rate constants are available. Moreover the non-Arrhenius behaviour of the hydrogen abstraction reactions considered in this work can, at least partly, be interpreted in terms of tunnelling of H atom through the potential barrier.Anglai