Document g2wLJnzjN99NZmreoYGobYXRe

AR226-3370 The Role of Photolysis in the Atmosp Fate of Perfluorinated Aldehydes: Phase UV and IR Absorption Spec Hashikawa, Y.1, Kawasaki, M.1, Sulbaek Andersen, M.2, N O.2, Hurley, M.3, Wallington, T.3, Waterland, R.4, 1 Kyoto University/ Kyoto, Japan 2 University of Copenhagen, Copenhagen, Denmark 3 Ford Motor Company, Dearborn, MI, USA 4 E. I. du Pont de Nemours & Co., Inc., Wilmington, DE, USA Abstract Long-chain perfluoroalkyi carboxylic acids (PFC been observed in remote locations and are presumed t atmospheric degradation products of precursor chemica Atmospheric oxidation of fluorotelomer alcohols (FTOH O^x+i0^1'^01'^ has been suggested as a possible so PFCAs. It is well established that perfluorinated aldeh (PFALs) are atmospheric oxidation products of FTOHs, subsequent fate of these aldehydes is unclear at this ti Since UV photolysis is likely to be an important process for PFALs, we have examined the UV and IR sp ^^x+i^0 (x=l-4) using computational and experime techniques, ntroduction Very recently, derivatives of perfluorooctanoi (PFOA, CyF^COOH) and of other perfluoroalkyi carboxylic acids (C^x+iCOOH, where x = 6 -12 been observed in trace quantities in fish [2,3] an mammals [4] in remote locations. Fluorotelomer alcohols, (FTOHs, CJ^+iCHzCH are chemical intermediates commonly used in th manufacture of fluorotelomer-based products an been suggested that atmospheric oxidation of FT may be a source of PFCAs in the environment [5 FTOHs: in the environm not be in water. Will not be in biota. Strongly sorbed to soil. s Observed in air, Atmospheric Fate of FTO FTOH Expect FTOH to travel 1000s (PFAL) A. It depends on what else is around: NOx and H A'. It depends on where you are: urban/suburban A. What else is around; NO.X.' A'. Where you are: urban/suburban. No perfluorinated acids form A. What else is around: HO^. A\ Where you are: remote regions. Some perfluorinated acids form Competition from photolys Do the fluoroaldehydes photolyze? If so, how does photolysis compete with ch pathways? C^n+iCHO + hv ----^ CnF^+i + - CHO ----^ C,F^iH+CO What is known: The normal aldehydes CnH^n+iCHO photodissociate (hours/days) by the corresponding pathways Experimental Materials & Meth C^x+iCHO (x=l-4) samples were synthesize Research and purified by vacuum distillation. UV spectra measured using a commercial dua UV spectrometer (Lambda 18, Perkin Elmer) ope spectral resolution of 1.0 nm. IR spectra were derived from 32 superposed interferograms measured using a Mattson Instru Sirius 100 FTIR spectrometer operated at a spec resolution of 0.50 cm-1, interfaced to a 140 liter, evacuable Pyrex chamber. Spectra were recorded at 296 K in the presen Torr of air diluent. Theoretical Methods All calculations were performed using the Ga 03 [6] suite of programs using the B3LYP fun UV Spectra Optimized geometries and frequencies were obtained using derived DZVP basis set. Vertical excitation energies and oscillator strengths were c with TD-DFT using the DZVP basis set augmented with Ry functions on all heavy atom centers. Energies were rescaled using E^ = IR Spectra 1.144Ecaic - 0.553 eV Geometries, frequencies and intensities obtained using B3L Frequencies were scaled by 0.961. Cross-section (10'20 cm2 molecule'1) NM-0-yiO -l M W 0 IM ft 0) Results: IR Spectra Lu^l_k A: C^PgCHO B: C3F,,CHO 750 1000 1250 1500 1750 2000 2250 2500 2750 3000 Wavenumber (cm'1) Figure 2 Discussion The PFALs C^F^+iCHO (x=l - 4), absorb strongl critical UV region above 290 nm. absorption is concentrated in a broad single band. for the higher aldehydes, the peak absorption is at anticipate that the higher homologues (x>4), will a very similar wavelength. absorption maximum increases monotonically and r increasing length of the perfluorinated tail. Peak ab C4FgCHOis about 3.5 times greater than that of CF3 The higher perfluoroalkyi aldehydes absorb more st the corresponding non-halogenated counterparts. PFALs will UV much th non-halogenated Discussion However, in the absence of quantum yield data unclear whether the rate of photolysisof long c perfluoroaldehydes is greater than, comparable than that of the corresponding normal aldehyde Studies of the photolysis quantum yields for C^ (x > 1) under atmospheric conditions are neede quantify the degree to which photolysis compet and perhaps eliminates, formation of perfluoroc acids by chemical pathways. References 1. J. W. Martin, M. M. Smithwick, B. M. Braune, P. F. Hoekstra, G.Muir, S. A. Mabury, Environ. Sci. Tech. 38, 373 (2004). 2. C. A. Moody, J. W. Martin, W. C. Kwan, D. C. G. Muir, S. A. M Environ. Sci. Tech., 36, 545 (2002). 3. C. A. Moody, W. C. Kwan, J. W. Martin, D. C. G. Muir, S. A. M Analytical Chemistry 73, 2200 (2001). 4. J. W. Martin, M. M. Smithwick, B. M. Braune, P. F. Hoekstra, Muir, S. A. Mabury, Environ. Sci. Tech. 38, 373 (2004). 5. D. A. Ellis, J. W. Martin, A. 0. De Silva, S. A. Mabury, M. D. H P. Sulbaek Andersen, T. J. WaUington, Environ. Sci. Tech. 38 (2004). 6. Gaussian 03, Revision B.05, M. J. Frisch et al., Gaussian, Inc. Pittsburgh PA, (2003). Acknowledgements Ole John Nielsen thanks the Danish Natural Science Research C for financial support. In addition, we thank Robert C. Buck, Pau Krusic and Mary A. Kaiser for their assistance in this work.