The F-+CH3I → FCH3 +I- entrance channel potential energy surface Comparison of electronic structure methods

Rui Sun, Jing Xie, Jiaxu Zhang, William L. Hase

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The potential energy surface (PES) of the F- + CH3I → FCH3 +I- Sn2 nucleophilic substitution reaction has been studied previously using MP2 and DFT levels of theory (J. Phys. Chem. A 2010,114,9635-9643). This work indicated that DFT gives a better representation of the PES which has only an hydrogen-bonded entrance channel reaction path, with a hydrogen-bonded transition state [F··HCH2··I]- connecting the hydrogen-bonded pre-reaction complex F-··· HCH2I and C3v post-reaction complex FCH3··· I-. For the work presented here, CCSD(T) with three different basis set and two effective core potentials (i.e. PP/d, PP/t and ECP/d) was employed to investigate stationary point properties for this reaction. Besides the hydrogen-bonded entrance channel stationary points, CCSD(T) also predicts a traditional C3v transition state [F··CH3·· I]- connecting a C3v pre-reaction complex F-·· CH3I with the C3v post-reaction complex FCH3 · · ·I-. Though CCSD(T) gives a CH3F···I- binding energy and CH3 F and CH3I geometries in almost exact agreement with experiment, it gives a heat of reaction ∼20 kJ/mol less exothermic than experiment. The MP2 PES for this reaction, determined in the previous study, is very similar to the CCSD(T), but obtained with a much smaller computational cost. Direct dynamics simulations for the F- + CH3I→ FCH3 +I- reaction are feasible with MP2.

Original languageEnglish
Pages (from-to)222-227
Number of pages6
JournalInternational Journal of Mass Spectrometry
Issue number1
StatePublished - 2015


  • Ion
  • Molecular dynamics simulation
  • Nucleophilic substitution reaction


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