关键词: 隧道效应, 动力学, 反应通道, 变分(数学), 过渡态, 反应途径, 有机硅化合物, 抽提反应, 反应速度常数

The abstraction of H with (CH3)2SiH2 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 G 2MP2 level was used for the final energy calculations. Theoretical analysis provided conclusive evidence that the main process occurring in this reaction is the abstraction of H from the Si-H bond leading to the formation of the H2 and silyl radical; the abstraction of H from C－H bond has higher barrier height and is difficult to react in this reaction. The kinetics of the title reaction has been studied by using the "direct dynamics" method of variational transition-state theory, which is based on the information on geometries, frequencies and energies calculated for ab initio along the minimum energy path. The rate constants of the title reaction were calculated for the range of temperture 298～1 000 K, In the calculation, we considered the tunneling correction. 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 ground-state (CD-SCSAG) method. The rate constants calculated match well with the experimental values.

Key words: TUNNELING EFFECT, DYNAMICS, VARIATION (MATHEMATICS), TRANSITION STATE, REACTION PATH, ORGANO SILICON COMPOUNDS, REACTION RATE CONSTANT