Acta Phys. -Chim. Sin. ›› 2010, Vol. 26 ›› Issue (01): 183-187.doi: 10.3866/PKU.WHXB20100132

• QUANTUM CHEMISTRY AND COMPUTATION CHEMISTRY • Previous Articles     Next Articles

Direct Ab initio Dynamics on the Reaction o fMethanethiol and Hydrogen Atom

WANG Yong-Xia, DUAN Xue-Mei, Wang Qin, LIU Jing-Yao   

  1. State Key Laboratory of Theoretical and Computational Chemistry, Institute of Theoretical Chemistry, Jilin University, Changchun 130023, P. R. China
  • Received:2009-09-25 Revised:2009-11-09 Published:2009-12-29
  • Contact: LIU Jing-Yao E-mail:ljy121@jlu.edu.cn

Abstract:

We studied the reaction of CH3SH+H theoretically using a dual-level direct dynamics method. Three reaction channels: two H-abstraction (from the —SH and —CH3 groups) and one substitution channels, were found. Optimized geometries, frequencies, and energies of the stationary points as well as extra points along the minimum energy path were calculated at the MP2/6-311+G(d, p) level of theory. The potential energy profiles were then refined by single-point energy calculations at the G3(MP2) level. Furthermore, the rate constants of all three channels were evaluated by canonical variational transition state theory (CVT) with the small-curvature tunneling effect correction (SCT) over the wide temperature range of 220-1000 K. These calculations show that H-abstraction from the —SH group (R1) is the major channel for the title reaction over the whole temperature range. The substitution channel (R3) is a minor pathway at low temperatures and becomes more important as the temperature increases. This would be a competitive channel at high temperature while the contribution of H-abstraction fromthe—CH3 group (R2) to the overall rate constant is almost negligible because of its high energy barrier. The calculated CVT/SCT rate constants agree well with the available experimental values. The three-parameter rate-temperature expression for the total reaction over the whole temperature range of 220-1000 K is shown to be k=5.00×10-18T2.39exp(-119.81/T), which may be a useful expression for future experiments.

Key words: Direct dynamics, Ab initio, G3(MP2), Rate constant, Canonical variational transition state theory

MSC2000: 

  • O641