Atmospheric Chemistry of CF_3C(O)OCH_2CF_3: UV Spectra and Kinetic Data for CF_3C(O)OCH(centre dot)CF_3 and CF_3C(O)OCH(OO centre dot)CF_3 Radicals, and Atmospheric Fate of CF_3C(O)OCH(O centre dot)CF_3 Radicals

摘要

Pulse radiolysis transient UV absorption spectroscopy was used to study the ultraviolet absorption spectra (230-330 nm) and kinetics of CF_3C(O)OCH(centre dot)CF_3 and CF_3C(O)OCH(OO centre dot)CF_3 radicals at 296 K. At 280 nm #sigma#(CF_3C(O)OCH(centre dot)CF_3) = (1.08 +- 0.13) * 10~(-18) cm~2 molecule~(-1), at 240 nm #sigma#(CF_3C(O)OCH(OO centre dot)CF_3) = (2.06 +- 0.24) * 10~(-18) cm~2 molecule~(-1). Rate constants for the reaction of F atoms with CF_3C(O)OCH(-2)CF_3, the self-reactions of CF_3C(O)OCH(centre dot)CF_3 and CF_3C(O)OCH(OO centre dot)CF_3 radicals, and the reactions of CF_3C(O)OCH(00 centre dot)CF_3 radicals with NO and NO_2 were (1.8 +- 0.2) * 10~(-12), (1.5 +- 0.2) * 10~(-11), (7.6 +- 0.9) * 10~(-12), (1.5 +- 0.2) * 10~(-11), and (8.5 +- 0.9) * 10~(-12) cm~3 molecule~(-1) s~(-1), respectively. The atmospheric fate of CF_3C(O)OCH(O centre dot)CF_3 radicals was investigated in a FTIR smog chamber. Three loss processes for the CF_3C(O)OCH(O centre dot)CF_3 radicals were identified at 296 K and 700 Torr total pressure, reaction with O_2 to form CF_3C(O)OC(O)CF_3, #alpha#-rearrangement to form CF_3C(O)centre dot radicals and CF_3C(O)OH, and decomposition via a mechanism which is unclear. In 760 Torr of air at 296 K, 65% of the CF_3C(O)OCH(O centre dot)CF_3 radicals react with oxygen, 18% undergo #alpha#-rearrangement, while the fate of the remaining 17% is unclear.