不同取代基对传统烯烃亲电加成反应机制的挑战  

Challenge of the Traditional Olefin Electrophilic Addition Reaction Mechanism Induced by Different Substituents

作　　者：刘永东[1] 王露红 钟儒刚[1] Liu Yongdong;Wang Luhong;Zhong Rugang(Faculty of Environment and Life,Beijing University of Technology,Beijing 100124,China)

机构地区：[1]北京工业大学环境与生命学部,北京100124

出　　处：《山东化工》2024年第2期168-170,共3页Shandong Chemical Industry

摘　　要：氯鎓离子是经典的烯烃与次氯酸亲电加成反应中的重要中间体,经过此中间体的分步反应机制是教学烯烃亲电加成反应中介绍的唯一反应机制。然而,量子化学计算结果表明,烯烃的不同取代基会导致反应机制发生变化。被一般供电基团和弱吸电基团取代的烯烃与次氯酸先形成氯鎓离子中间体,再生成马氏产物;而当取代基具有与C=C双键形成p-π或π-π共轭的供电基团时,反应生成的是碳正离子中间体。中和强吸电基团取代的烯烃分别通过协同和亲核加成反应机制与次氯酸反应,生成反马氏产物。由此可见,教学烯烃亲电加成反应机制时,不能局限在传统的氯鎓离子中间体机制,关注机制的适用体系是非常必要的。Chloronium ion is an important intermediate in the traditional electrophilic addition reaction between olefins and hypochlorite,and it is the only reaction mechanism taught in class regarding the olefin electrophilic addition reaction.However,quantum chemistry calculation results indicate that different substituents of olefins cause the changes of the electrophilic addition reaction mechanism.Ethylene substituted with general electron donating groups(EDGs)and weak electron withdrawing groups(EWGs)reacts with HOCl via the traditionally believed chloronium ion intermediate to generate Markovnikov products,in which carbon-cation intermediate yields for substituents being EDGs featuring p-πorπ-πconjugation with the C=C moiety of olefin.When the substituents are moderate and strong EWGs,the olefins prefer the Anti-Markovnikov products through the concerted and the new nucleophilic addition reaction mechanisms,respectively.Therefore,it is very necessary to pay attention to the applicable system of the mechanism rather than the traditional chloronium ion intermediate mechanism,when teaching the mechanism of olefin electrophilic addition.

关 键 词：亲电加成反应 反应机制 氯鎓离子 

分 类 号：O621[理学—有机化学]