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Atmospheric chemistry of HFE-7200 (C4F9OC2H5): Reaction with OH radicals and fate of C4F9OCH2CH2O(•) and C4F9OCHO(•)CH3 radicals

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  • L. K. Christensen
  • J. Sehested
  • Nielsen, Ole John
  • M. Bilde
  • T. J. Wallington
  • A. Guschin
  • L. T. Molina
  • M. J. Molina

Relative rate techniques were used to measure k(OH + n-C4F9OC2H5) = (6.4 ± 0.7) × 10-14 and k(OH + i-C4F9OC2H5) = (7.7 ± 0.8) × 10-14 cm3 molecule-1 s-1 at 295 K leading to estimates of ≈0.9 and 0.7 years for the atmospheric lifetimes of n-C4F9OC2H5 and i-C4F9OC2H5, respectively. A pulse radiolysis technique was used to measure k(F + HFE-7200) = (5.6 ± 2.1) × 10-11 cm3 molecule-1 s-1 (HFE-7200 = C4F9-OC2H5) at 296 K. Using FTIR-smog chamber relative rate techniques the following rate constants were determined at 296 K: k(F + HFE-7200) = (5.5 ± 1.1) × 10-11, k(Cl + HFE-7200) = (2.7 ± 0.6) times; 10-12, and k(Cl + C4F9OC(O)CH3) < 7 × 10-13 cm3 molecule-1 s-1. Two competing loss mechanisms for C4F9-OCHO(•)CH3 radicals were identified in 700 Torr of N2/O2 diluent at 296 K; reaction with O2 and decomposition via C-C bond scission with kO2/kdecomp = 0.026 ± 0.010 Torr-1. The Cl atom initiated oxidation of HFE-7200 in N2/O2 diluent gives two products: C4F9OC(O)CH3 and C4F9OC(O)H. C4F9OC(O)CH3 is the major atmospheric oxidation product of HFE-7200; C4F9OC(O)H is a minor product. The results are discussed with respect to the atmospheric chemistry of hydrofluoroethers.

OriginalsprogEngelsk
TidsskriftJournal of Physical Chemistry A
Vol/bind102
Udgave nummer25
Sider (fra-til)4839-4845
Antal sider7
ISSN1089-5639
StatusUdgivet - 18 jun. 1998

ID: 225753691