丙二烯和乙烯环加成机理的理论研究

Theoretical Study on the Cycloaddition of Propadiene with Ethyene

用半经验分子轨道理论AM1方法,研究了丙二烯和乙烯[2+2]环加成反应机理,结果表明,乙烯的碳原子既可以进攻丙二烯的中间碳原子,也可以进攻其端碳原子,反应先经过第一过渡态生成中间体,再越过第二过渡态后生成产物。反应的速控制步骤为生成中间体的第一步,反应位垒约为23kcal/mol,与实验结果相吻合.

The reaction mechanism of [2+2] cycloaddition of propadiene with ethylene has been studied by semi-empirical M.O. theory AM1 method. The results show that ethylene can attack either the middle or the terminal carbon atom of propadiene. The reaction proceeds via two steps.The reactions will first pass a transition state structure and produce an intermediate, and then pass the second transition state structure to produce the product. The rate determining step is the first one, and the activation barrier is about 23 kcal/ mol, which is in accordance with experimental data.