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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.
Bimodal nucleophilic (SN2) reaction is one of the most important basic organic reactions, in which the transfer of electrons from the nucleophilic group to the leaving group plays a key role.Using ab initio method CCSD (T) / aug-cc-pVDZ And the theory of the molecular topography developed by us, we study the reaction of F- + CH3Cl → CH3F + Cl- and give the dynamic change of molecular shape and electron transfer during the reaction. The results show that along the intrinsic reaction coordinate, After the reaction started to generate the pre-reaction complex, the molecular intrinsic characteristic profile of the nucleophilic reagent F- was slowly contracting while its electron density was slowly increasing. Thereafter, the profile of F expanded rapidly and the electron density dropped sharply, especially From the transition state to the product of the complex process, while in the reaction process, the leaving group Cl has been shrinking the profile of its electron density has been increasing. The reaction process of the electron potential by the potential , With the progress of the reaction, the potential applied by the electrons in F and C gradually decreased, while the potential acting on C and Cl gradually increased, clearly showing the formation of chemical bonds between F and C and the formation of C and Cl The dynamic process of chemical bond cleavage.