Product distribution and mechanism of the OH− initiated tropospheric degradation of three CFC replacement candidates: CH3CFCH2, (CF3)2CCH2 and (E/Z)-CF3CFCHF

Abstract

The OH radical initiated photodegradation of 2-fluoropropene (CH₃CFCH₂), 3,3,3-trifluoro-2-(tri-fluoromethyl)propene ((CF₃)₂CCH₂) and (E/Z)-1,2,3,3,3-pentafluoropropene ((E/Z)-CF₃CFCHF) has been investigated for the first time using a 1080 L quartz-glass environmental chamber at 298 ± 2 K and atmospheric pressure of synthetic air coupled with in situ FTIR spectroscopy to monitor reactants and products. The major products observed in the OH reaction were CH₃C(O)F (98 ± 5)% together with HC(O)H (89 ± 7)% as a co-product, CF₃C(O)F (103 ± 8)% together with HC(O)F (96 ± 7)% as a co-product and CF₃C(O)CF₃ (91 ± 8)% together with HC(O)H (98 ± 12)% as a co-product from the C₁–C₂ bond cleavage channel of the intermediate hydroxyalkoxy radical, formed by addition of OH to the terminal carbon of the double bond which is designated C₁ of 2-fluoropropene, (E/Z)-1,2,3,3,3-pentafluoropropene and 3,3,3-trifluoro-2-(tri-fluoromethyl)propene, respectively. The present results are compared with previous studies for the reaction of OH with the separate isomers (E) and (Z) of 1,2,3,3,3-pentafluoropropene. In addition, atmospheric implications of the reactions studied are discussed.