物理化学学报 >> 2012, Vol. 28 >> Issue (05): 1120-1126.doi: 10.3866/PKU.WHXB201203082

理论与计算化学 上一篇    下一篇

F-+CH3Cl→CH3F+Cl-反应过程中的分子形貌变化

张明波1,2, 宫利东2   

  1. 1. 辽宁中医药大学药学院, 辽宁大连 116600;
    2. 辽宁师范大学化学化工学院, 辽宁大连 116029
  • 收稿日期:2011-12-27 修回日期:2012-03-07 发布日期:2012-04-26
  • 通讯作者: 宫利东 E-mail:gongjw@lnnu.edu.cn
  • 基金资助:

    国家自然科学基金(21133005, 21073080, 21011120087, 20703022)资助项目

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 E-mail:gongjw@lnnu.edu.cn
  • Supported by:

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

摘要: 双分子亲核(SN2)反应是重要的基本有机反应之一, 其中电子从亲核基团向离去基团的转移发挥着关键作用. 利用从头计算方法CCSD(T)/aug-cc-pVDZ和我们发展的分子形貌理论, 对反应F-+CH3Cl→CH3F+Cl-进行了研究, 给出了反应过程中分子形状和电子转移的动态变化图像. 结果表明, 沿内禀反应坐标, 从反应开始到生成反应前复合物, 亲核试剂F-的分子内禀特征轮廓在缓慢收缩, 而其上的电子密度在缓慢增大. 此后, F的轮廓迅速膨胀, 电子密度急剧下降, 尤其是从过渡态到产物复合物的过程中. 而在反应过程中, 离去基团Cl 的轮廓一直在收缩, 其上的电子密度一直在增大. 对反应过程中电子所受到作用势的研究表明, 随着反应的进行, 电子在F与C间受到的作用势逐渐降低, 而在C与Cl 间受到的作用势逐渐升高, 清楚地展现反应过程中F与C间化学键生成和C与Cl 间化学键断裂的动态过程.

关键词: 从头计算, 分子形貌理论, SN2反应, 电子转移, 反应机理

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

MSC2000: 

  • O641