C_2h_3自由基与O_2反应机理的量子化学研究

用量子化学从头计算中UMP2(full)方法优化了C_2H_3自由基与O_2反应通道上 驻点（反应物、中间体、过渡态和产物）的几何构型，在Gaussian-3(G3)水平上计 算了它们的能量。在此基础上计算了该反应通道上各基元反应的反应活化能。通过 我们的研究发现，C_2H_3自由基与氧气反应存在着三元环、四元环和五元环反应机 理，且分别生成不同的产物，从反应活化能的计算结果扯CH_2O和CHO是反应的主要 产物，其次还可能生成CH_3 + CO_2, CH_2CO_2 + H, C_2H_2 + O_2H和COHCOH + H等产物，且它们生成几率逐渐减少，我们对生成产物CH_2O + CHO, CH_3 + CO_2, C_2H_2 + O_2H和COHCOH + H四条反应通道化学反应热的计算结果与实验吻 合较好。

Quantum Chemical Study on the Mechanism for the Reaction of C_2H_3 Radical with O_2

Ab initio UMP2(full) method has been used to study the mechanism for the reaction of C_2H_3 radical with O_2 on the potential energy surface. Energies have been calculated at Gaussian-3(G3) level. In this paper, we have optimized the geometry configuration of reactants, productions, intermediates and transition states. We have also calculated the activation energies of elementary reactions along the reaction pathways. The results suggest that the reaction mechanism of this reaction involves the formation of three-member, fourmember and five-member rings and produces different reaction resultants respectively. According to the calculated activation energies, the CH_2O and CHO are the main productions. At the same time, the reaction may form CH_3 + CO_2, CH_2CO_2 + H, C_2H_2 + O_2H and COHCOH + H, etc. The probabilities gradually decrease. The reaction heats gained in our study along the four pathways (C_2H_3 + O_2 →CH_2O + CHO, C_2H_3 + O_2 → CH_3 + CO_2, C_2H_3 + O_2 → C_2H_2 + O_2H and C_2H_3 + O_2 → OHCOH + H) are in good agreement with those of experiments.