| Autor: |
Sulbaek Andersen MP; Department of Chemistry and Biochemistry, California State University Northridge, 18111 Nordhoff St., Northridge, California 91330-8262, United States.; Copenhagen Center for Atmospheric Research, Department of Chemistry, University of Copenhagen, Universitetsparken 5, Frederiksberg, Copenhagen Ø DK-2100, Denmark., Borcher JE; Copenhagen Center for Atmospheric Research, Department of Chemistry, University of Copenhagen, Universitetsparken 5, Frederiksberg, Copenhagen Ø DK-2100, Denmark., Blair C; Department of Chemistry and Biochemistry, California State University Northridge, 18111 Nordhoff St., Northridge, California 91330-8262, United States., Robin ML; The Chemours Company, 1007 Market Street, Wilmington, Delaware 19899, United States., Nielsen OJ; Copenhagen Center for Atmospheric Research, Department of Chemistry, University of Copenhagen, Universitetsparken 5, Frederiksberg, Copenhagen Ø DK-2100, Denmark. |
| Abstrakt: |
Smog chamber experiments were conducted to establish the atmospheric chemistry of ( E )- and ( Z )-CF 3 CF 2 CH═CHCF 2 CF 3 . Kinetics of the reactions of the two compounds with Cl atoms and OH radicals were measured using relative rate techniques, giving k (Cl + ( E )-CF 3 CF 2 CH═CHCF 2 CF 3 ) = (5.63 ± 0.84) × 10 -12 , k (Cl + ( Z )-CF 3 CF 2 CH═CHCF 2 CF 3 ) = (1.17 ± 0.20) × 10 -11 , k (OH + ( E )-CF 3 CF 2 CH═CHCF 2 CF 3 ) = (1.64 ± 0.21) × 10 -13 , and k (OH + ( Z )-CF 3 CF 2 CH═CHCF 2 CF 3 ) = (3.13 ± 0.38) × 10 -13 cm 3 molecule -1 s -1 in 680 Torr air/N 2 /O 2 diluents at 296 ± 2 K. Rate coefficients for the reactions with O 3 , k (O 3 + ( E )-CF 3 CF 2 CH═CHCF 2 CF 3 ) ∼ 1 × 10 -22 and k (O 3 + ( Z )-CF 3 CF 2 CH═CHCF 2 CF 3 ) ≤ 5× 10 -24 cm 3 molecule -1 s -1 , were established using absolute techniques in a 680 Torr air diluent and 296 ± 2 K. The Cl reaction with ( E )-CF 3 CF 2 CH═CHCF 2 CF 3 gives CF 3 CF 2 CHClC(O)CF 2 CF 3 as the sole oxidation product, whereas the reaction with ( Z )-CF 3 CF 2 CH═CHCF 2 CF 3 also gives rise to the formation of the ( E )-isomer in minor yields. The reaction of OH radicals with CF 3 CF 2 CH═CHCF 2 CF 3 gives CF 3 CF 2 CHO in a yield of 177 ± 17%. The main atmospheric fate of ( E ) - and ( Z )-CF 3 CF 2 CH═CHCF 2 CF 3 is the reaction with OH radicals, resulting in overall atmospheric lifetime estimates of 71 and 37 days, for ( E )- and ( Z )-CF 3 CF 2 CH═CHCF 2 CF 3 , respectively. The IR absorption cross sections are reported, and the global warming potentials of ( E )- and ( Z )-CF 3 CF 2 CH═CHCF 2 CF 3 for the 20-, 100-, and 500-year time horizons are calculated to be 36, 10, and 3 for the ( E ) - isomer and 11, 3, and 1 for the ( Z )-isomer, respectively. Atmospheric processing of ( E )- and ( Z )-CF 3 CF 2 CH═CHCF 2 CF 3 is expected to yield CF 3 CF 2 COOH and CF 3 COOH in yields of <10%. This study provides a comprehensive description of the atmospheric chemistry and fate of ( E )- and ( Z )-CF 3 CF 2 CH═CHCF 2 CF 3 . |
