Direct ab initio molecular dynamics study on a SN2 reaction OH− + CH3Cl → CH3OH + Cl−: Effect of non-zero impact parameter on the reaction dynamics

Direct ab initio molecular dynamics (MD) calculations have been applied to a SN2 reaction OH− + CH3Cl → CH3OH + Cl−. The collision dynamics with non-zero impact parameters were treated in the present study, and the results are compared with the near collinear collision dynamics previously reported by us [H. Tachikawa, M. Igarashi, T. Ishibashi, J. Phys. Chem. A 106 (2002) 10977]. The collision energy was fixed to 25 kcal/mol. The product state distribution obtained for the non-zero impact parameter collision dynamics was slightly different from that of the collinear collision. The distribution of relative translational energy between products Cl− and CH3OH in the non-zero impact parameter collision dynamics was shifted to higher energy region from that of collinear collision. Also, it was found that the mean translational energy of the product has a maximum at non-zero impact parameter (b = 0.6-1.2 Å). The reaction mechanism is discussed on the basis of theoretical results.