氟乙烯与氧分子的反应机理分析

DFT analysis for reaction mechanism of CH_2=CHF with O_2

不饱和的氯氟烃可能与空气中的氧分子直接反应生成原子氧,抑制臭氧分解为氧分子和氧原子的过程进行,从而保护臭氧层。本文通过研究不饱和氯氟烃的代表物CH_2=CHF与单线态和三线态氧分子的反应机理,讨论其直接与氧分子反应生成氧原子的可能性及相关的反应和产物。在B3LYP/6-311++G(d,p)水平上,对CH_2=CHF和O_2反应及相关过程进行了计算和分析,具体包括:优化反应物、过渡态、中间体以及产物的几何构型;通过振动分析,确认过渡态、中间体以及产物;从过渡态出发进行内禀坐标(IRC)计算:反应体系中各基元反应的标准Gibbs自由能变计算;并通过零点能校正计算反应活化能。由此得出:氟乙烯与单线态氧分子反应生成的产物中有原子氧、乙酰氟、HF、CH_2=C=O、CH_3F、CO、氟乙醛,其中最稳定的产物是乙酰氟和氧原子;CH_2=CHF与氧分子反应生成抑制臭氧分解平衡的氧原子是可以自发进行的。

The unsaturated chlorofluorocarbons （CFCs） may directly react with oxygen molecules to produce atomic oxygen, and lead to the process of ozone decomposition into oxygen molecules and oxygen atoms to be inhibited. Thus, the ozone layer is protected. In this paper, at the B3LYP/6-31 l＋＋G（d, p） level based on density functional theory（DFT）, the geometry configurations of reactants, products, intermediates and transition states are optimized, and all of the above geometry configurations are verified by the vibrational analysis, and the elementary reaction are verified by the intrinsic reaction coordinate（IRC） calculation, and the standard Gibbs free energy change and activation energy through zero point correction for each elementary reaction have been calculated, also. The main results are summed： the products of the reaction between CHz=CHF and singlet oxygen molecule are O（1D）, CH3CFO, HF, CHz=C=O, CO, CH3F, CH2FCHO, and H2COCHF, in which the most stable ones are CH3CFO and O（1D）; CHE=CHF would react spontaneously with oxygen molecules to produce oxygen atoms, thus it can inhibit the ozone from dissociating efficiently.