Dynamics and Novel Mechanisms of SN2 Reactions on ab Initio Analytical Potential Energy Surfaces

István Szabó, G. Czakó

Research output: Contribution to journalArticle

32 Citations (Scopus)

Abstract

We describe a novel theoretical approach to the bimolecular nucleophilic substitution (SN2) reactions that is based on analytical potential energy surfaces (PESs) obtained by fitting a few tens of thousands high-level ab initio energy points. These PESs allow computing millions of quasi-classical trajectories thereby providing unprecedented statistical accuracy for SN2 reactions, as well as performing high-dimensional quantum dynamics computations. We developed full-dimensional ab initio PESs for the F- + CH3Y [Y = F, Cl, I] systems, which describe the direct and indirect, complex-forming Walden-inversion, the frontside attack, and the new double-inversion pathways as well as the proton-transfer channels. Reaction dynamics simulations on the new PESs revealed (a) a novel double-inversion SN2 mechanism, (b) frontside complex formation, (c) the dynamics of proton transfer, (d) vibrational and rotational mode specificity, (e) mode-specific product vibrational distributions, (f) agreement between classical and quantum dynamics, (g) good agreement with measured scattering angle and product internal energy distributions, and (h) significant leaving group effect in accord with experiments.

Original languageEnglish
Pages (from-to)9005-9019
Number of pages15
JournalJournal of Physical Chemistry A
Volume121
Issue number47
DOIs
Publication statusPublished - Nov 30 2017

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

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