中文摘要：

采用Gaussian09ONIOM分层计算方法,研究了全氟辛酸（C7F15COOH）热分解消除HF的反应历程,在B3LYP/aug-cc-pvtz//B3LYP/6-31G（d,p）＋ZPVE水平下,得到7条可能的反应通道.计算结果表明,全氟辛酸的热降解反应可以通过六元环反应机理、五元环反应机理、直接脱CO、CO2、CF2反应机理平行进行得到产物,其中以五元环过渡态进行反应生成CO、CF3（CF2）5CFO具有相对较低的活化能,为反应的主要通道,生成产物CO2和CF3（CF2）4CF=CF2的产率较低;PFOA的H异构化后经过五元环过渡态消除HF分子并形成环氧中间体,此过程能垒高达183.4kJ/mol,相较于其他各步能垒最高,为整个反应的速控步骤,理论预测的主要产物与实验基本吻合.研究还表明,强酸性条件有利于PFOA的降解.

英文摘要：

Perfluorooctanoic acid （PFOA ）,as a typical perfluorinated compounds,is one kind of emerging persistent pollutants appearing in natural water.It is of theoretical guiding significance to research the degradation mechanism of PFOA for experimentally exploring effective degradation methods. The mechanism of elimination hydrogen fluoride from PFOA was studied by Gaussian09 ONIOM layered calculation method.Seven possible reaction channels are obtained at the B3LYP/aug-cc-PVTZ//B3LYP/6-31G（d,p）＋ZPVE levels.The results show that the thermal degradation reaction of PFOA can proceed through the six-membered ring mechanism,five-membered ring mechanism,direct CO/CO 2/CF2 elimina-tion mechanism.The process of generating CO and CF3 （CF2 ）5 CFO via a five-membered ring transition state has relatively low activation energy,thus becoming the main channel for reaction,but the production rate of CO 2 and CF3 （CF2 ）4 CF=CF2 is low.The rate-determining step is the process of eliminating HF and forming a epoxy intermediate for the H-isomerized product of PFOA through five-membered ring transi-tion state with the energy barrier of 183.4 kJ/mol.Theoretical prediction of the main product is consistent with the experimental results.The results also show that the strong acidic conditions are beneficial to the degradation of PFOA.