Tropospheric Reaction Products and Mechanisms of the Hydrochlorofluorocarbons 141b, 142b, 225ca, and 225cb

1,1,1,3,3,-pentafluorobutane (HFC-365mfc): atmospheric degradation and contribution to radiative forcing

“…Previous work from this laboratory has shown that the generation of CF 3 O from the photolysis of CF 3 O 2 CF 3 in air gives high yields of CF 2 O in the presence of Cl atoms [37]. Generation of CF 2 O in the present system is consistent with the exothermic reactions (26) or (27). (26) (27) Abstraction of a hydrogen atom may also occur from the !…”

Tropospheric Degradation Products of Hydrochlorofluorocarbons and Hydrofluorocarbons

“…Figure 4 shows the spectra recorded from the photolysis of an air mixture with 2.6 x 10 16 molecule cm" 3 of CF 2 C1CH 3 and 1.3 x 10 14 molecule cm 3 of Cl 2 . The aldehyde product, CF 2 C1CH0, was positively identified by the exact correspondence of its C=0 stretch band (1778.6 cm' 1 ) with that of the prepared sample (7). In addition to the expected formation of C(0)F 2 , CF 2 C1C(0)0H was also observed as a product.…”

“…With the time-concentration data obtained and the rate constant ratio k(Cl + CFCl 2 CHO)/k(Cl + CFC1 2 CH 3 ) = 2600 ± 700, derived from published rate constants (17-19), corrections for the secondary reaction of CFCl 2 CHO with the the CI atom were calculated. The result was a 100% yield of CFCl 2 CHO from CFC1 2 CH 3 (7), indicating that at 298 K and atmospheric pressure of air the haloalkoxy radical CFC1 2 CH 2 6 does not decompose but solely reacts with 0 2 .…”

“…Because of the difficulty of maintaining high OH radical concentrations and the low rate constants for the OH radical reactions with the HCFCs and HFCs (9) reactions were initiated by reaction with CI atoms Cl 2 + hv -* 2 CI CI + RH -> HC1 + R The initial reactant concentrations (in molecule cm" 3 units) were typically: HCFC or HFC, (1.2-2.5) x 10 14 ; Cl 2 , (1. [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] x 10 14 ; although a series of experiments to measure the formation yields of CF 2 C1CH0 and CFCl 2 CHO from CF 2 C1CH 3 (HCFC-142b) and CFC1 2 CH 3 (HCFC-141b) used initial HCFC and Cl 2 concentra tions of (4.9-25.6) x 10 15 molecule cm' 3 and 1.3 x 10 14 molecule cm 3 , respectively (7). Most experiments were carried out at 298 ± 2 K and 740 Ton* total pressure of synthetic air (80% N 2 + 20% N^; experiments with CH 2 FCF 3 (HFC-134a) were carried out over the temperature range 273-320 K and with the 0 2 partial pressure and total pressure varied over the ranges 150-600 Torr and 150-740 Torr, respectively (5).…”

“…Samples of the highest purity available for CFC1 2 CH 3 and CF 2 C1CH 3 (>99.99%, Solvay S.A.) were employed. Authentic samples of CFCl 2 CHO and CF 2 ClCHO were prepared and purified in the authors' laboratory (7).…”