摘要
用量子化学从头算方法对CH2 Cl与OH自由基反应生成HCCl+H2 O、HCOCl+H2 和H2 CO +HCl的机理进行了研究 .在UMP2 (FC) / 6 311++G 水平上计算出了各物种的优化构型、振动频率 ;并在Gaussian 3(G3)水平上计算了他们的零点能 (ZPE)、相对能量及总能量 .结果表明 ,CH2 Cl和OH自由基反应首先经无垒过程生成一个富能中间体CH2 ClOH ,中间体再经过一系列原子转移、基团旋转和键断裂分别生成产物HCCl+H2 O、HCOCl+H2 和H2 CO +HCl;三者均为放热反应 ,放热量分别为 72 .81、338.5 4和 35 4 .0 8kJ/mol;生成H2 CO +HCl放出的热量比生成HCCl+H2 O放出的热量多 2 81.2 7kJ/mol,与实验结果吻合 .
The reaction mechanism of CH_2Cl radical with OH radical to produce HCCl+H_2O, HCOCl+H_2 and H_2CO+HCl has been studied by using quantum chemistry ab initio calculations. The optimized geometrical parameters, and vibrational frequencies of all species were obtained at the UMP2(FC) level of theory in conjunction with 6-311++G* basis set. Besides, the zero-point energies (ZPE), relative energies and total energies of all species were calculated using Gaussian-3(G3) model. The results of theoretical study indicate that the activated intermediate CH_2ClOH is first formed through a barrierless process, followed by atoms migration, radical groups rotation and bonds fission to produce HCCl+H_2O, HCOCl+H_2 and H_2CO+HCl, respectively. And all channels are exothermic by 72.81, 338.54 and 354.08 kJ/mol. The reaction heat of reactants to H_2CO+HCl is 281.27 kJ/mol more than that of reactants to HCCl+H_2O. This result accords with that of experiments.
基金
ProjectsupportedbytheNationalNaturalScienceFoundationofChina (2 0 0 730 4 2 ) .
