Theoretical studies on H with (CH3)(2)SiH2 abstraction reaction

The abstraction of H with (CH3)(2)SiH2 has been investigated at high levels of ab initio molecual orbital theory. Geometries were optimized at the MP - 2 level with 6 - 31G(d) basis set, and G2MP2 level was used for the final energy calculations. Theoretical analysis provided conclusive evidence tha t the main process occurring in this reaction is the abstraction of H from the Si-H bond leading to the formation of the H-2 and silyl radical; the ab straction of ii from C-H bond has higher barrier height and is difficult to react in this reaction. The kinetics of the title reaction has been studie d by using the "direct dynamics" method of variational transition - state t heory, which is based on the information on geometries, frequencies and ene rgies calculated for ab initio along the minimum energy path. The rate cons tants of the title reaction were calculated for the range of temperture 298 similar to 1 000 K. In the calculation, we considered the tunneling correc tion. Since the heavy - light - heavy mass - combination is not present in this hydrogen transfer reaction, the tunneling correction was calculated by using the centrifugal - dominant small curvature semiclassical adiabatic g round state (CD - SCSAG) method. The rate constants calculated match well w ith the experimental values.