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The relative-rate technique has been used to determine the rate coefficient for the reaction of C x F 2x+1 CH CH 2 (x = 1, 2, 3, 4 and 6) with ozone at (298 ± 2) K and (720 ± 5) Torr of air by FTIR (Fourier Transform Infrared Spectroscopy) and by GC-MS/SPME (Gas Chromatography-Mass Spectroscopy with Solid Phase Micro Extraction) in two different atmospheric simulation chambers. The following rate coefficients, in units of 10 −19  cm 3 molecule −1 s −1 , were obtained: (3.01 ± 0.10) for CF 3 CH CH 2 , (2.11 ± 0.35) for C 2 F 5 CH CH 2 , (2.34 ± 0.42) for C 3 F 7 CH CH 2 , (2.05 ± 0.31) for C 4 F 9 CH CH 2 and (2.07 ± 0.39) for C 6 F 13 CH CH 2 , where uncertainties represent ±2σ statistical error. The atmospheric lifetime of C x F 2x+1 CH CH 2 due to reaction with ozone was estimated from the reported rate coefficients. Additionally, the gaseous products formed in these reactions were investigated in the presence of synthetic air simulating a clean atmosphere. Perfluoroaldehydes, C x F 2x+1 C(O)H (PFALs), formaldehyde, formic acid and CF 2 O were identified as reaction products in the investigated reactions. The identified products made possible to propose a reaction mechanism that justifies the observed products. The atmospheric implications of these results are discussed in terms of the potential contribution of the atmospheric degradation of these species to PFAL and PFCA burden. [ABSTRACT FROM AUTHOR]

Rate coefficients for the gas-phase reactions of C x F 2x+1 CHCH 2 (x = 1, 2, 3, 4 and 6) with Cl atoms were determined at (298 ± 2) K and (710 ± 5) Torr of air using a relative rate technique. Two experimental setups with simulation chambers were employed with Fourier Transform Infrared (FTIR) spectroscopy and Gas Chromatography coupled to Mass Spectrometry (GC-MS) as detection techniques. The Cl-rate coefficients obtained were (in 10 -10  cm 3  molecule -1  s -1 ): (0.85 ± 0.11) for CF 3 CHCH 2 , (1.11 ± 0.08) for C 2 F 5 CHCH 2 , (1.12 ± 0.18) for C 3 F 7 CHCH 2 , (0.97 ± 0.09) for C 4 F 9 CHCH 2 , and (0.99 ± 0.08) for C 6 F 13 CHCH 2 . Additionally, the gas-phase products were identified and quantified, when possible, by FTIR spectroscopy or GC-MS. The main reaction product was reported to be C x F 2x+1 C(O)CH 2 Cl. The fluorinated species, C x F 2x+1 CHO and C x F 2x+1 C(O)CH 2 Cl, were identified. CF 3 C(O)CH 2 Cl and CF 3 CHO were found to be formed with molar yield of (69 ± 5)% and (9 ± 1)%, respectively. The global lifetime of the investigated C x F 2x+1 CHCH 2 due to their Cl-reaction is more than 100 days so this route does not compete with the removal by OH radicals. This lifetime is long enough for C x F 2x+1 CHCH 2 to be transported to remote areas where they can be degraded. However, at a local scale, in marine regions at dawn the removal of C x F 2x+1 CHCH 2 is expected to occur in ca. 1 day. The atmospheric degradation of these hydrofluoroolefins by Cl atoms is not expected to be a source of bioaccumulative perfluorinated carboxylic acids, C x F 2x+1 C(O)OH. Additionally, the UV absorption cross sections of CF 3 C(O)CH 2 Cl were determined together with the rate coefficient of the OH reaction by an absolute kinetic method at room temperature., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Hydrofluoroolefins (HFOs) of the type CF3(CF2)x≥0CHCH2, are currently being suggested as substitutes of some hydrofluorocarbons (HFCs). In this work, an assessment of the atmospheric removal of CF3(CF2)x=1,3,5CHCH2, initiated by reaction with hydroxyl (OH) radicals and UV solar radiation is addressed. For that purpose, the rate coefficients for the OH + CF3(CF2)x=1,3,5CHCH2 reaction, kOH(T = 263-358 K), were determined by the pulsed laser photolysis-laser induced fluorescence technique. A slightly negative temperature dependence of kOH was observed, obtaining Ea/R (in K) values of -124 ± 15, -128 ± 6 and -160 ± 10, for CF3CF2CHCH2, CF3(CF2)3CHCH2 and CF3(CF2)5CHCH2, respectively. The estimated atmospheric lifetimes are around 8 days, considering that HFOs are well-mixed in the troposphere. Furthermore, an evaluation of the long-wave and short-wave absorption process of these HFOs have been carried out by determining the UV (191-367 nm) and IR (4000-500 cm(-1)) absorption cross sections at 298 K. Based on the obtained UV absorption cross sections, no photolysis of CF3(CF2)x=1,3,5CHCH2 is expected in the troposphere (λ > 290 nm). These species strongly absorb IR radiation in the atmospheric IR window. Despite the strong absorption in the IR region, the lifetime corrected radiative efficiencies are low (0.033 W m(-2) ppb(-1) for CF3(CF2)3CHCH2 and 0.039 Wm(-2) ppb(-1) for CF3(CF2)5CHCH2). Calculation of GWPs for these species has been performed as a function of the horizon time, providing values higher than unity for a short-period term, decreasing dramatically for longer periods. Therefore, it is concluded that emissions of these species do not affect the radiative forcing of climate, making them suitable replacements of large-GWP HFCs., (Copyright © 2016. Published by Elsevier Ltd.)