邻基参与反应历程探讨

Discussion of Neighboring Group Participation in Reaction Course

邻基参与反应的历程主要有三类 ,即n—参与历程、π—参与历程和σ—参与历程 ;分为二步 :( 1)反应物的邻基从反面进攻α—碳原子 ,形成中间体 ,构型转化一次 ,为分子内的SN2反应 ;( 2 )外部的亲核试剂Nu—从邻基的反面进攻中间体 ,构型又转化一次 ,再发生一次分子内SN2反应 ,其结果是 :该类反应总的来说属于SN1反应历程 。

There are three kinds of neighboring group participation in reaction course, which is n—participation course and o—participation course. They are divided into two steps: neighboring group of response matter attacks α—carbon atom from reverse side, takes shape into intermediate, and the type transforms once, which is S_(N)2 reaction in molecule; outside nucleophile Nu^(—) attacks the intermediate from reverse side of neighboring group, the type transforms once again, and S_(N)2 reaction in molecule happens once again. The result is that, this kind of reaction generally belongs to S_(N)1 reaction course, and the type of production keeps intact.