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用从头计算-解析梯度法研究了亚甲基环丙烷卡宾的重排反应。开环重排经Hückel型过渡态,在过渡态前后分别属2电子和4电子反应,取对旋和顺旋方式,遵从4n+2和4n规则。1,2氢重排经迁移氢进攻卡宾碳的空p轨道发生。用RHF/6-31-G¨∥STO-3G方法算得开环势垒为24 kJ/mol。1,2氢重排不是开环的竞争反应,其势垒为118 kJ/mol。与环丙烷卡宾比较,亚甲基取代未改变其开环反应的类型与机理,但增大开环反应活性。
Rearrangement of methylenecyclopropanecarbene was studied by ab initio calculation - analytical gradient method. The ring-opening rearrangements are Hückel-type transition states, which are 2-electron and 4-electron reactions before and after the transition state, respectively, and adopt the rules of 4n + 2 and 4n. Hydrogen rearrangement of 1,2 hydrogen takes place by empty hydrogen orbitals that attack the carbene carbon. The open-loop barrier was calculated to be 24 kJ / mol using the RHF / 6-31-G¨ // STO-3G method. 1,2 hydrogen rearrangement is not a ring-opening competitive reaction with a barrier of 118 kJ / mol. Compared with cyclopropane carbene, methylene substitution did not change the type and mechanism of its ring-opening reaction, but increased the ring-opening reactivity.