Benchmark ab Initio Characterization of the Complex Potential Energy Surfaces of the X- + NH2Y [X, y = F, Cl, Br, I] Reactions

Bálint Hajdu, G. Czakó

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

We report a comprehensive high-level explicitly correlated ab initio study on the X- + NH2Y [X,Y = F, Cl, Br, I] reactions characterizing the stationary points of the SN2 (Y- + NH2X) and proton-transfer (HX + NHY-) pathways as well as the reaction enthalpies of various endothermic additional product channels such as H- + NHXY, XY- + NH2, XY + NH2 -, and XHY- + NH. Benchmark structures and harmonic vibrational frequencies are obtained at the CCSD(T)-F12b/aug-cc-pVTZ(-PP) level of theory, followed by CCSD(T)-F12b/aug-cc-pVnZ(-PP) [n = Q and 5] and core correlation energy computations. In the entrance and exit channels we find two equivalent hydrogen-bonded C1 minima, X-⋯HH′NY and X-⋯H′HNY connected by a Cs first-order saddle point, X-⋯H2NY, as well as a halogen-bonded front-side complex, X-⋯YNH2. SN2 reactions can proceed via back-side attack Walden inversion and front-side attack retention pathways characterized by first-order saddle points, submerged [X-NH2-Y]- and high-energy [H2NXY]-, respectively. Product-like stationary points below the HX + NHY- asymptotes are involved in the proton-transfer processes.

Original languageEnglish
Pages (from-to)1886-1895
Number of pages10
JournalJournal of Physical Chemistry A
Volume122
Issue number7
DOIs
Publication statusPublished - Feb 22 2018

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

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