氰基丙二烯与乙烯环加成机理的理论研究

Theoretical Study on the Cycloaddition of-CN Substituted Propadiene with Ethylene

应用ＡＭ１方法研究了氰基丙二烯和乙烯环加成反应的反应机理，讨论了氰基对反应机理的影响．结果表明乙烯和氰基丙二烯之间的反应是自由基反应，乙烯进攻氰基丙二烯的中心碳原子从能量上考虑比进攻两端碳原子更为有利，且位垒比丙二烯上无取代基时低，比氨基取代时高，说明吸电子基团氰基取代氢原子后，使环加成反应易于进行，但没有供电子基团氨基的作用大。以上结论均与实验结果一致。

Semi-empirical MO theory AM1 method has been used to investigate the[2+2]cycloaddition of-CN substituted propadiene with ethylene.The results show that this reaction can proceed through three possible paths:(1)ethylene reacts with the central carbon of-CN substituted propadiene;(2)ethylene reacts with the terminal carbon attached and(3)not attached with-CN group. Path(1)has a relatively lower activation barrier than that of(2)and(3).The activation barrier of(1)is lower than that of the cycloaddition of ethylene with-NH2 substituted propadiene,The three paths all involve intermediate radicals.