环氧乙烷均聚反应机理的理论研究  

Investigations on Polymerization Mechanism of Ethylene Oxide

作　　者：张治国[1] 尹红[1] 陈志荣[1] 

机构地区：[1]浙江大学联合化学反应工程研究所,杭州310027

出　　处：《化学学报》2004年第20期1988-1992,F005,共6页Acta Chimica Sinica

基　　金：国家科技攻关计划 (No.2 0 0 3BA757C 2 );浙江省科技计划 (No.2 0 0 4C31 0 58)资助项目

摘　　要：借助量子化学理论计算方法对环氧乙烷均聚反应历程进行了理论探讨 .采用DFT中的B3LYP方法在 6 3 11G 基组下对环氧乙烷基态和激发态以及亲核试剂和亲电试剂进攻环氧乙烷反应产物进行几何构型全优化 ,确定了各物种的电子结构、电荷分布和键长等参数 .运用前线轨道理论从微观电子结构层次上对环氧乙烷的各种均聚反应机理进行了分析 ,探讨了阳离子均聚和阴离子均聚机理的合理性 .由于受到前线轨道对称性和能级差的限制 ,环氧乙烷的基态分子不能发生均聚 ,同样也不能发生自由基均聚 ;而当环氧乙烷基态分子被亲电试剂或亲核试剂进攻时 ,可以进一步生成新的亲电或亲核试剂从而引发环氧乙烷均聚 .Quantum chemical method was employed to investigate the mechanism of polymerization of ethylene oxide. The electronic structure, charge distribution and bond length of ethylene oxide in ground and excited states and the products of the reaction of ethylene oxide with electrophiles, and nucleophiles were investigated theoretically at the B3LYP/6-311G* * level. The mechanism of polymerization of ethylene oxide was discussed on the basis of electronic microstructures. By analysis of their frontier orbitals, the reasonability of the cationic and anionic polymerization mechanism of ethylene oxide was confirmed theoretically. Due to symmetrical properties of frontier orbitals and energy difference of bonding orbitals, the radical polymerization of ethylene oxide can not proceed. However the products of the reaction of ethylene oxide with electrophiles and nucleophiles could react with ethylene oxide, resulting in the possibility of polymerization. The cationic ring-opening polymerization involved the nucleophilic attack of monomer on the oxonium ion, in which instead of ring-opening on monomer, ethylene oxide was activated and ready for addition reaction and side reaction. The anionic ring-opening polymerization proceeded by nucleophilic attack of the propagating anion on monomer, in which ring-opening on ethylene oxide was undertaken. Calculation results satisfactorily explained the experimental facts.

关 键 词：环氧乙烷 均聚反应 反应机理 非离子表面活性剂 前线轨道 

分 类 号：O631.5[理学—高分子化学]