Product distribution in the Cl-initiated photooxidation of CF3C(O)OCH2CF3

The product distribution and the mechanism of the reaction of Cl atoms with 2,2,2-trifluoroethyl 2,2,2-trifluoroacetate (TFETFA; CF3C(O)OCH2CF3) were investigated using a 1080 L environmental chamber with in situ Fourier transform infrared (FTIR) spectroscopy detection. The experiments were performed at (296 +/- 2) K and atmospheric pressure (760 +/- 10) Torr of synthetic air free of NOx. A yield of (45 +/- 3)% was obtained for the CF3C(O)OC(O)CF3 formation. CF2O and CO were produced with estimated yields of 35 and 28%, respectively. No trifluoroacetic acid (TFA; CF3C(O)OH) was observed. The yields determined are rationalized in terms of the competitive reaction channels for the fluoroalcoxy radicals formed in the H-abstraction process: (a) reaction with O-2, (b) C-C, C-O, C-H decomposition, and (c) a possible alpha-ester rearrangement pathway. The negligible importance of the alpha-ester channel, to produce TFA, was explained by the reduction of the stability of the five-membered transition state of the alpha-ester rearrangement. Atmospheric implications, particularly regarding the fluorocarboxylic acid formation, are discussed. Copyright (C) 2010 John Wiley & Sons, Ltd.