卤素与乙烯、取代乙烯的亲电加成反应的量子化学研究

Quantum Chemical Study on the Electrophilic Additions of Halogens to Ethylene and Substituted Ethylenes

用MNDO法及能量梯度法优化了F^(+)、Ci^(+)与乙烯、丙烯、氟乙烯亲电加成反反的中间体,得到最稳定的构型。结果表明,氯比氟容易生成环式中间体,取代的乙烯比不取代的更易生成开式中间体。用基于从头算(4-31G基组)的Morokuma方案分解以F^(+)为进攻试剂的三个体系的相互作用能。此反应中电荷迁移是最重要的相互作用,其次是静电相互作用。分析了上述两种取代基对相互作用能的影响。

The various intermediates of elcctrophilic additions of F^(+),Cl^(+) to ethylcne,propene,fluorocthylene have been optimized by MNDO scheme with energy gradient technique.The most stable configurations were obtained.The substituted ethylenes tend to form the open intermediates more easily than the cthylene but the Cl^(+) as the reagent,tends to form the cyclic intermediate more easily than the F^(+).The interaction energies of the above three systems with F^(+) as electrophile have been studied further with ab initio method and E were decomposed into their components by Morokuma’s decomposition scheme.In these reactions,it is found that charge transfer interaction is the most important one while the electrostatic interaction is the next.The effects of the substituting groups were also discussed.