Atmospheric Chemistry of HFC-227ca: Spectrokinetic Investigation of the CF3CF2CF2O2 Radical, Its Reactions with NO and NO2, and the Atmospheric Fate of the CF3CF2CF2O Radical

A pulse radiolysis technique was used to study the UV absorption spectrum of CF 3 CF 2 CF 2 O 2 radicals, at 230 nm σ = (3.2 ± 0.4) × 10 -18 cm 2 molecule -1 . Rate constants for reactions of CF 3 CF 2 CF 2 O 2 radicals with NO and NO 2 were k 3 > 7 × 10 -12 cm 3 molecule -1 s -1 and k 4 = (7.6 ± 2.4) × 10 -12 cm 3 molecule -1 s -1, respectively. The rate constant for reaction of F atoms with CF 3 CF 2 CF 2 H was determined by using an absolute rate technique to be (3.6 ± 1.3) × 10 -13 cm 3 molecule -1 s -1 . The atmospheric fate of CF 3 CF 2 CF 2 O radicals is decomposition via C−C bond scission to give CF 3 CF 2 radicals and CF 2 O. In one bar of SF 6 at 296 K, CF 3 CF 2 CF 2 O radicals decompose with a rate > 1.5 × 10 5 s -1 . In their turn CF 3 CF 2 radicals are converted into CF 3 CF 2 O radicals which also decompose via C−C bond scission. As part of this work a relative rate method was used to measure k (Cl + CF 3 CF 2 CF 2 H) = (3.4 ± 0.7) × 10 -16 and k (F + CF 3 CF 2 CF 2 H) = (3.2 ± 0.8) × 10 -13 cm 3 molecule -1 s -1 . The results are discussed with respect to the atmospheric chemistry of HFC-227ca.