Han Junbin, Lu Zhichao, Hammond Gerald B, Xu Bo
Department of Chemistry, University of Louisville, Louisville, KY 40292, USA.
College of Chemistry, Chemical Engineering and Biotechnology, Donghua University, Shanghai 201620, China.
iScience. 2020 Sep 21;23(10):101593. doi: 10.1016/j.isci.2020.101593. eCollection 2020 Oct 23.
Ionic reactions are the most common reactions used in chemical synthesis. In relatively low dielectric constant solvents (e.g., dichloromethane, toluene), ions usually exist as ion pairs. Despite the importance of counterions, a quantitative description of how the paired 'counterion' affects the reaction kinetic is still elusive. We introduce a general and quantitative model, namely transition-state expansion (TSE), that describes how the size of a counterion affects the transition-state structure and the kinetics of an ionic reaction. This model could rationalize the counterion effects in nucleophilic substitutions and gold-catalyzed enyne cycloisomerizations.
离子反应是化学合成中最常用的反应。在相对低介电常数的溶剂（如二氯甲烷、甲苯）中，离子通常以离子对的形式存在。尽管抗衡离子很重要，但关于成对的“抗衡离子”如何影响反应动力学的定量描述仍然难以捉摸。我们引入了一个通用的定量模型，即过渡态扩展（TSE），该模型描述了抗衡离子的大小如何影响离子反应的过渡态结构和动力学。该模型可以解释亲核取代反应和金催化的烯炔环异构化反应中的抗衡离子效应。
