Galano Annia
Instituto Mexicano del Petróleo, Eje Central LAzaro CArdenas 152, 007730 México D. F., México.
J Phys Chem A. 2007 Jun 14;111(23):5086-91. doi: 10.1021/jp0708345. Epub 2007 May 17.
A theoretical study on the mechanism of the OH reactions with HCN and CH(3)CN, in the presence of O2, is presented. Optimum geometries and frequencies have been computed at BHandHLYP/6-311++G(2d,2p) level of theory for all stationary points. Energy values have been improved by single-point calculations at the above geometries using CCSD(T)/6-311++G(2d,2p). The initial attack of OH to HCN was found to lead only to the formation of the HC(OH)N adduct, while for CH(3)CN similar proportions of CH(2)CN and CH(3)C(OH)N are expected. A four-step mechanism has been proposed to explain the OH regeneration, experimentally observed for OH + CH(3)CN reaction, when carried out in the presence of O2. The mechanism steps are as follows: (1) OH addition to the C atom in the CN group, (2) O2 addition to the N atom, (3) an intramolecular H migration from OH to OO, and (4) OH elimination. This mechanism is in line with the one independently proposed by Wine et al. for HCN. The results obtained here suggest that for the OH + HCN reaction, the OH regeneration might occur even in larger extension than for OH + CH(3)CN reaction. The agreement between the calculated data and the available experimental evidence on the studied reactions seems to validate the mechanism proposed here.
本文介绍了在O₂存在的情况下，OH与HCN和CH₃CN反应机理的理论研究。已在BHandHLYP/6 - 311++G(2d,2p)理论水平上计算了所有驻点的最佳几何结构和频率。通过在上述几何结构上使用CCSD(T)/6 - 311++G(2d,2p)进行单点计算，提高了能量值。发现OH对HCN的初始攻击仅导致形成HC(OH)N加合物，而对于CH₃CN，预计CH₂CN和CH₃C(OH)N的比例相似。提出了一种四步机理来解释在O₂存在下进行OH + CH₃CN反应时实验观察到的OH再生。机理步骤如下：(1) OH加成到CN基团中的C原子上，(2) O₂加成到N原子上，(3) 分子内H从OH迁移到OO上，以及(4) OH消除。该机理与Wine等人独立提出的HCN机理一致。此处获得的结果表明，对于OH + HCN反应，OH再生可能比OH + CH₃CN反应发生得更为广泛。计算数据与所研究反应的现有实验证据之间的一致性似乎验证了本文提出的机理。
