Overtone-Induced Degradation of Perfluorinated Alcohols in the Atmosphere

详细信息    查看全文

• 作者：Cora J. Young ; D. J. Donaldson
• 刊名：Journal of Physical Chemistry A
• 出版年：2007
• 出版时间：December 27, 2007
• 年：2007
• 卷：111
• 期：51
• 页码：13466 - 13471
• 全文大小：122K
• 年卷期：v.111,no.51(December 27, 2007)
• ISSN：1520-5215

文摘

Perfluorinated alcohols (PFOHs) are thermally unstable and degrade via loss of HF, ultimately formingperfluorocarboxylic acids. Experiments and calculations of the high activation barrier for the decompositionof CF₃OH suggest that the reaction occurs exclusively heterogeneously, perhaps with the involvement ofwater. Here, we use density functional theory calculations to show that PFOHs may readily complex withwater and are expected to be present as a few percent of the total PFOH concentration under ambientatmospheric conditions. The presence of water lowers the HF elimination barrier sufficiently that excitationto low-lying O-H vibrational overtone levels (v_OH 3) may cause reaction. Photolysis rate constants forCF₃OH·H₂O and CF₃CF₂OH·H₂O were estimated to be 6.1 × 10^-8 and 5.6 × 10^-8 s^-1, respectively. PFOH-water complexes should undergo degradation much faster than the corresponding gas-phase unimoleculardecomposition of PFOHs, which requires excitation into the v_OH = 5 or 6 vibrational level. Overtone-drivengas-phase reactions of PFOH-water complexes could be moderately competitive with heterogeneous reactionswith water in dry locations. Overtone-induced degradation of PFOHs is likely a modest atmospheric sourceof PFCAs to the environment.