High-level analytical potential-energy-surface-based dynamics of the OH− + CH3CH2Cl SN2 and E2 reactions in full (24) dimensions

Abstract

We develop a coupled-cluster full-dimensional global potential energy surface (PES) for the OH⁻ + CH₃CH₂Cl reactive system, using the Robosurfer program package, which automatically samples configurations along PES-based trajectories as well as performs ab initio computations with Molpro and fitting with the monomial symmetrization approach. The analytical PES accurately describes both the bimolecular nucleophilic substitution (S_N2) and elimination (E2) channels leading to the Cl⁻ + CH₃CH₂OH and Cl⁻ + H₂O + C₂H₄ products, respectively, and allows efficient quasi-classical trajectory (QCT) simulations. QCT computations on the new PES provide accurate statistically-converged integral and differential cross sections for the OH⁻ + CH₃CH₂Cl reaction, revealing the competing dynamics and mechanisms of the S_N2 and E2 (anti, syn, β–α transfer) channels as well as various additional pathways leading to induced inversion of the CH₃CH₂Cl reactant, H-exchange between the reactants, H₂O⋯Cl⁻ complex formation, and H₂O + CH₃CHCl⁻ products via proton abstraction.