Product distribution and mechanism of the OH − initiated tropospheric degradation of three CFC replacement candidates: CH 3 CF═CH 2 , (CF 3 ) 2 C═CH 2 and (E/Z)-CF 3 CF═CHF

Abstract

The OH radical initiated photodegradation of 2-fluoropropene (CH 3 CF═CH 2 ), 3,3,3-trifluoro-2-(tri-fluoromethyl)propene ((CF 3 ) 2 C═CH 2 ) and (E/Z)-1,2,3,3,3-pentafluoropropene ((E/Z)-CF 3 CF═CHF) 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 CH 3 C(O)F (98 ± 5)% together with HC(O)H (89 ± 7)% as a co-product, CF 3 C(O)F (103 ± 8)% together with HC(O)F (96 ± 7)% as a co-product and CF 3 C(O)CF 3 (91 ± 8)% together with HC(O)H (98 ± 12)% as a co-product from the C 1 -C 2 bond cleavage channel of the intermediate hydroxyalkoxy radical, formed by addition of OH to the terminal carbon of the double bond which is designated C 1 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.