论文部分内容阅读
应用量子化学方法对偶氮异丁腈(AIBN)在基态下的热分解反应机理进行了系统的理论研究.首先用AM1方法对AIBN的各种可能解离的势能面(PES)进行详细的优化扫描,进而运用密度泛函方法B3LYP在6-311G水平上对热解反应过程中所涉及的反应物、中间体、产物和过渡态的几何构型、内禀反应坐标(IRC)以及活化能和振动分析进行计算.结果表明,在基态下,偶氮异丁腈仅采取两键(三体)同步解离的模式进行热分解反应,即Me2(CN)C—N=N—C(CN)Me2u001f2Me2(CN)C+N2,产物形成N2和Me2(CN)C纷杂苫?而单键的热分解Me2(CN)CN=N—C(CN)Me2u001fMe2(CN)CN=N+Me2(CN)C凡荒芊⑸?这主要是由于偶氮异丁腈分子中(—N=N—)的电子收缩效应,使Me2(CN)CN=N方徊缴赡芰拷系偷腘2和稳定自由基Me2(CN)C的缘故.按AIBN双键(三体)同步解离获得的活化能与实验结果吻合,并从理论上计算得到两键(三体)同步解离的反应途径.
A quantum chemical method was used to systematically study the thermal decomposition mechanism of AIBN in ground state.At first, a detailed and optimized scanning of the potential energy surface (PES) of AIBN with AM1 method , And then use the density functional method B3LYP at 6-311G level on the pyrolysis reaction involved in the reactants, intermediates, product and transition state geometry, intrinsic reaction coordinate (IRC) and activation energy and vibration The results show that in the ground state, azo-isobutyronitrile only takes the mode of simultaneous two-bond (trisomic) dissociation for thermal decomposition, that is, Me2 (CN) C-N = N-C (CN) C + N2, the product forms N2 and Me2 (CN) C complex and the thermal decomposition of one bond Me2 CN CN = N-C CN CN2 N + Me2 (CN) C where the shortage 芊 ⑸? This is mainly due to the azo isobutyronitrile molecules (-N = N-) electronic shrinkage effect, so that Me2 (CN) CN =腘 2 and the stable radical Me2 (CN) C. The activation energy obtained by simultaneous dissociation of AIBN double bonds (trisomy) is consistent with the experimental results, and the theoretical calculation of the simultaneous dissociation of the two bonds Reaction pathway