Atmospheric chemistry of Z- and E-CF 3 CHCHCF 3

Abstract

The first determination of the atmospheric chemistry of E -CF 3 CHCHCF 3 and of the Cl and O 3 initiated atmospheric chemistry of Z -CF 3 CHCHCF 3 . The atmospheric fates of Z - and E -CF 3 CHCHCF 3 have been studied, investigating the kinetics and the products of the reactions of the two compounds with Cl atoms, OH radicals, OD radicals, and O 3 . FTIR smog chamber experiments measured: k (Cl + Z -CF 3 CHCHCF 3 ) = (2.59 ± 0.47) × 10 −11 , k (Cl + E -CF 3 CHCHCF 3 ) = (1.36 ± 0.27) × 10 −11 , k (OH + Z -CF 3 CHCHCF 3 ) = (4.21 ± 0.62) × 10 −13 , k (OH + E -CF 3 CHCHCF 3 ) = (1.72 ± 0.42) × 10 −13 , k (OD + Z -CF 3 CHCHCF 3 ) = (6.94 ± 1.25) × 10 −13 , k (OD + E -CF 3 CHCHCF 3 ) = (5.61 ± 0.98) × 10 −13 , k (O 3 + Z -CF 3 CHCHCF 3 ) = (6.25 ± 0.70) × 10 −22 , and k (O 3 + E -CF 3 CHCHCF 3 ) = (4.14 ± 0.42) × 10 −22 cm 3 molecule −1 s −1 in 700 Torr of air/N 2 /O 2 diluents at 296 ± 2 K. E -CF 3 CHCHCF 3 reacts with Cl atoms to give CF 3 CHClC(O)CF 3 in a yield indistinguishable from 100%. Z -CF 3 CHCHCF 3 reacts with Cl atoms to give (95 ± 10)% CF 3 CHClC(O)CF 3 and (7 ± 1)% E -CF 3 CHCHCF 3 . CF 3 CHClC(O)CF 3 reacts with Cl atoms to give the secondary product CF 3 C(O)Cl in a yield indistinguishable from 100%, with the observed co-products C(O)F 2 and CF 3 O 3 CF 3 . The main atmospheric fate for Z - and E -CF 3 CHCHCF 3 is reaction with OH radicals. The atmospheric lifetimes of Z - and E -CF 3 CHCHCF 3 are estimated as 27 and 67 days, respectively. IR absorption cross sections are reported and the global warming potentials (GWPs) of Z - and E -CF 3 CHCHCF 3 for the 100 year time horizon are calculated to be GWP 100 = 2 and 7, respectively. This study provides a comprehensive description of the atmospheric fate and impact of Z - and E -CF 3 CHCHCF 3 .