The abstraction reaction of H with SiH2Cl2 has been investigatedat high levels of ab initio molecule orbital theory. Geometries have been optimized at the UMP2(FULL) level with 6-31G(d) basis set, and G2MP2 level have been used for the final energy calculation. Theoretical analysis provides a conclusive evidence that the main process occurring in this reaction is the abstraction of H from the Si-H bond; the abstraction of Cl has higher barrier and is difficult to react. The kinetic or the title reaction has been studied by using the "direct dynamics" method of canonical variational transition- state theory (CVT) with small curvature tunneling effect (SCT), which is based on the information on geometries, frequencies and energies calculated using ab initio method along the minimum energy path. The changes of the important kinetic parameters along the reaction coordinate have been discussed. The rate constants of the title reaction have been calculated over the temperature range of 200～ 1000K. The CVT/SCT rate constant exhibit typical non-Arrhenius behavior, a three-parameter rate- temperature formula is fitted in units of cm^3·molecule^-1· s^-1 as follows: k(T)=(1.32×10^-22)T^3. 67exp(-26/T). The calculated CVT/SCT rate constants match well with the experimental values.

Key words: HYDROGEN ATOM, TRANSITION STATE THEORY, DYNAMICS, CHLOROSILANE, EXTRACTION