An application of the rotating line umbrella model to quantum dynamics of SN2 reactions

The rotating line umbrella (RLU) model has been modified to study quantum scattering of the SN2 reaction A+CH3B ⇌ ACH3+B. The RLU model treats three internal physical variables: the two reactive A–C and B–C bonds and the umbrella mode. Time-independent quantum scattering calculations were performed in hyperspherical coordinates. Boundary conditions were applied using a hyperspherical projection method. As a numerical example, the Cl− + CH3Cl → ClCH3 + Cl− reaction is treated. Scattering resonances play an important role in the dynamics. Exciting the Cl–CH3 stretch vibration enhances the reaction significantly, while the umbrella mode has only a small effect.