Wu Zemin, Rong Chunying, Lu Tian, Ayers Paul W, Liu Shubin
Key Laboratory of Chemical Biology and Traditional Chinese Medicine Research (Ministry of Education of China), College of Chemistry and Chemical Engineering, Hunan Normal University, Changsha Hunan 410081, China.
Phys Chem Chem Phys. 2015 Oct 28;17(40):27052-61. doi: 10.1039/c5cp04442a. Epub 2015 Sep 28.
As a continuation of our recent efforts to quantify chemical reactivity with quantities from the information-theoretic approach within the framework of density functional reactivity theory, the effectiveness of applying these quantities to quantify electrophilicity for the bimolecular nucleophilic substitution (SN2) reactions in both gas phase and aqueous solvent is presented in this work. We examined a total of 21 self-exchange SN2 reactions for the compound with the general chemical formula of R1R2R3C-F, where R1, R2, and R3 represent substituting alkyl groups such as -H, -CH3, -C2H5, -C3H7, and -C4H9 in both gas and solvent phases. Our findings confirm that scaling properties for information-theoretic quantities found elsewhere are still valid. It has also been verified that the barrier height has the strongest correlation with the electrostatic interaction, but the contributions from the exchange-correlation and steric effects, though less significant, are indispensable. We additionally unveiled that the barrier height of these SN2 reactions can reliably be predicted not only by the Hirshfeld charge and information gain at the regioselective carbon atom, as previously reported by us for other systems, but also by other information-theoretic descriptors such as Shannon entropy, Fisher information, and Ghosh-Berkowitz-Parr entropy on the same atom. These new findings provide further insights for the better understanding of the factors impacting the chemical reactivity of this vastly important category of chemical transformations.
作为我们近期在密度泛函反应性理论框架内，利用信息论方法中的量来量化化学反应性工作的延续，本文展示了将这些量应用于量化气相和水相中双分子亲核取代（SN2）反应亲电性的有效性。我们总共研究了通式为R1R2R3C-F的化合物的21个自交换SN2反应，其中R1、R2和R3在气相和溶剂相中均代表取代烷基，如-H、-CH3、-C2H5、-C3H7和-C4H9。我们的研究结果证实，在其他地方发现的信息论量的标度性质仍然有效。还证实了势垒高度与静电相互作用的相关性最强，但交换相关和空间效应的贡献虽然较小，但不可或缺。我们还发现，这些SN2反应的势垒高度不仅可以像我们之前针对其他体系所报道的那样，通过区域选择性碳原子上的Hirshfeld电荷和信息增益可靠地预测，还可以通过同一原子上的其他信息论描述符，如香农熵、费舍尔信息和戈什-伯科维茨-帕尔熵来预测。这些新发现为更好地理解影响这一极其重要的化学转化类别化学反应性的因素提供了进一步的见解。
