Since Fluoroesters (FESs) are known products of the atmospheric oxidation of some Hydrofluorinated ethers (HFEs)1, it is necessary to obtain a full understanding of the atmospheric chemistry of FESs in order to evaluate the environmental suitability of HFEs compared to other potential replacement compounds of CFCs, HFCs and HCFCs. The gas-phase removal processes of FESs include OH, NO3, Cl reactions and other process like dissolution in clouds and seawater2,3. In recent years the oxidations of volatile organic compounds (VOCs) by the highly reactive chlorine atom has gained much attention mainly in the marine troposphere where significant chlorine atom concentration may be present 4.
In this work we report the kinetic study, for the reactions of Cl atoms with methyl trifluoroacetate (CF3C(O)OCH3), ethyl trifluoroacetate (CF3C(O)OCH2CH3), methyl difluoroacetate (CF2HC(O)OCH3) and 2,2,2-trifluoroethyl trifluoroacetate (CF3C(O)OCH2CF3). The relative rate constants were measured by following the simultaneous losses of the
The following rate coefficients (in units of cm3 molecule-1s-1) have been obtained for the reactions of FESs with Cl atoms: k (methyl trifluoroacetate) = (0.90 ± 0.30) × 10-13, k (ethyl trifluoroacetate) = (1.78 ± 0.57) × 10-12, k (methyl difluoroacetate) = (2.03 ± 0.65) × 10-13 and k (2,2,2-trifluoroethyl trifluoroacetate) = (1.18 ± 0.43) × 10-15. No previous experimental rate constant values have been found for the reactions of the studied FESs with Cl atoms except for 2,2,2-trifluoroethyl trifluoroacetate5. Our experimental value of rate coefficient is in very good agreement with the value reported by Wallington et al.
The reactivity of Fluoroesters towards Cl atoms is compared with other saturated VOCs and a correlation with the reactivity towards OH radicals is discussed. Finally, an estimation of the gas-phase lifetime for the esters studied in the marine boundary layer may be obtained from the kinetic data obtained in this work.
