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.
Bibliographical noteFunding Information:
This material is based upon work supported by the Robert A. Welch Foundation under grant D-0005 . The authors acknowledge the Texas Advanced Computing Center (TACC) at The University of Texas at Austin for providing HPC resources that have contributed to the research results reported within this paper (URL: http://www.tacc.utexas.edu ). Jiaxu Zhang acknowledges financial support from the Institute of Chemistry, Chinese Academy of Sciences ( No. CMS-PY-201316 ). Support was also provided by the High-Performance Computing Center (HPCC) at Texas Tech University (TTU) , under the direction of Philip W. Smith, and the TTU Department of Chemistry & Biochemistry cluster Robinson, whose purchase was funded by the National Science Foundation under the CRIF-MU Grant No. CHE-0840493 . The authors also wish to thank Branko Ruscic for helpful comments.
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- Molecular dynamics simulation
- Nucleophilic substitution reaction