F,Cl原子与臭氧和甲烷反应机理和反应动力学的理论研究

用量子化学从关计算UMP2（full)方法研究F和Cl原子与甲烷分子和臭氧之间的反应机理，优化了反应物、产物、中间体和过渡态的几何构型，在Gaussian-3(G3)和G3MP2水平计算了它们的能量，研究结果表明：F原子与Cl原子一样与臭氧之间有很强的反应活性，而F原子与甲烷分子反应过程中有氢键生成，键能为3.71KJ/MOL，F原子与甲烷分子之间反应活性比与臭氧分子之间反应活性强。F原子易与甲烷分子生成含有氢键的化合物，且很快分解生成化学性质非常稳定的HF，能同F O3反应竞争，而CL原子甲烷分子反应过程中则无氢键生成现象，且在CL原子与臭氧和甲烷之间竞争反应时，CL原子与臭氧之间反应优先，同时我们还对F和CL原子与甲烷分子臭氧之间反应动力学速率常数进行了计算，我们的理论计算结果能合理地解释大气中CL原子是损耗臭氧的主要化学物质，而活性更强的F原子为什么对臭氧损耗较小的原因。

Theoretical Study on the Reaction Mechanism and Kinetics of Fluorine and Chlorine Atoms with Ozone and Methane

Ab initio UMP2(full) method was performed to study the reaction mechanism of F and Cl atoms with methane and ozone. The geometry configurations of reactants, products, intermediates and transition states were optimized at UMP2(full)/6-31G * level and the energies of stationary points along the pathways were calculated at Gaussian-3(G3) and G3MP2 level. The results show that fluorine atoms react with ozone as violently as chlorine atoms; during the process of the reaction F+CH 4, the hydrogen bond forms, the bond energy is 3.71 kJ/mol. In addition, fluorine atoms react readily with methane to form the intermediate with a hydrogen bond, which easily decomposed to form HF with stable properties. That is to say, the reaction F+CH 4 is prior to the reaction F+O 3 when there is a competition between methane and ozone. However, there is no hydrogen bond in the reaction Cl+CH 4, and the reaction Cl+O 3 is prior to Cl+CH 4 when there is a competition between methane and ozone. Besides, we have calculated the rate constants of the fluorine and chlorine atoms with methane and ozone reactions. Therefore we can reasonably explain why chlorine atoms are the main reactants depleting ozone, while the more active fluorine atoms deplete less ozone.