Acta Phys. -Chim. Sin. ›› 2012, Vol. 28 ›› Issue (05): 1120-1126.doi: 10.3866/PKU.WHXB201203082


Evolution of the Molecular Face during the Reaction Process of F-+CH3Cl→CH3F+Cl-

ZHANG Ming-Bo1,2, GONG Li-Dong2   

  1. 1. College of Pharmacy, Liaoning University of Traditional Chinese Medicine, Dalian 116600, Liaoning Province, P. R. China;
    2. School of Chemistry and Chemical Engineering, Liaoning Normal University, Dalian 116029, Liaoning Province, P. R. China
  • Received:2011-12-27 Revised:2012-03-07 Published:2012-04-26
  • Contact: GONG Li-Dong
  • Supported by:

    The project was supported by the National Natural Science Foundation of China (21133005, 21073080, 21011120087, 20703022).

Abstract: Bimolecular nucleophilic substitution (SN2) reactions are among the fundamental organic reactions, in which electron transfer from the nucleophilic group to the leaving group plays an essential role. We use a high-level ab initio CCSD(T)/aug-cc-pVDZ method in conjunction with our previouslydeveloped molecular face (MF) theory, to investigate the SN2 reaction F-+CH3Cl→CH3F+Cl-. Dynamic representations of molecular shape evolution and electron transfer features throughout the reaction are vividly presented. It is found that along the intrinsic reaction coordinate (IRC), from the beginning of the reaction to the prereaction complex, the molecular intrinsic characteristic contour (MICC) of the nucleophile (F-) contracts slowly, while the electron density on the MICC increases slowly. The MICC of F then expands quickly, and the electron density decreases sharply, especially from the transition state to the product complex. However, for the leaving group (Cl), the MICC contracts, and the electron density increases all along the reaction. Investigations of the potential acting on an electron in a molecule (PAEM) show that, as the reaction progresses, the PAEM gradually decreases between fluorine and carbon, while it gradually increases between carbon and chlorine. This study enhances our understanding of the dynamic processes of bond-forming between F and C atoms and bond-breaking between C and Cl atoms.

Key words: Ab initio calculation, Molecular face theory, SN2 reaction, Electron transfer, Reaction mechanism


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