Insights into the bond-selective reaction of Cl + HOD(n(OH)) → HCl + OD.

Bond-selective reaction dynamics of the title reaction is investigated using full-dimensional quantum dynamical (QD) and quasi-classical trajectory (QCT) methods on a newly constructed ab initio global potential energy surface. Both QD and QCT results indicate that excitation of the local OH vibration in the HOD reactant renders the reaction strongly bond selective, with the OD/OH branching ratio in quantitative agreement with the experiment. In addition, the reactivity is found to be greatly enhanced with the reactant vibrational excitation, thanks to the change of a direct rebound mechanism to a capture mechanism. The QCT calculations also yield product state distributions, which show that the HCl product is vibrationally and rotationally hot while the OD co-product is internally cold. The bond selectivity, vibrational enhancement, and product energy disposal are rationalized by the Sudden Vector Projection model.