Temperature dependence of hydrogen transfer reactions via tunneling at low temperatures

Abstract

Abstract In this paper, we present a symmetrical and adiabatic reaction path for hydrogen transfer from methane by methyl by an ab initio method using the 6‐31 G ** basis set with the MP 2 corrections for UHF /6–31 G ** optimized geometries. The theoretical barrier is fitted with the symmetric Eckart function. We, then, take thermal averages of the rate constant ( k ) considering the discrete nature of the C–H oscillators and the continuous character of the various low‐frequency modes of the composite system. Finally, we present a linear relation between log k and temperature. It is shown that this relation gives a good description of the kinetic results of both thermal and photochemical H‐transfer reactions in the region of low temperatures. © 1993 John Wiley & Sons, Inc.