Kinetics of the reaction of OH radical with ethylfluoroacetate, ethyl 4,4,4-trifluorobutyrate, and butylfluoroacetate

Abstract

Kinetics of the gas-phase reactions of OH radicals with a series of fluoroesters were studied for the first time at (298 ± 3) K and atmospheric pressure. Relative rate coefficients were determined by in situ FTIR spectroscopy in nitrogen and GC-FID in air to monitor the decay of reactants and references. The following coefficient values (in 10-12 cm3molecule-1s-1) were obtained for ethyl fluoroacetate (EFA), ethyl 4,4,4-trifluorobutyrate (ETB), and butyl fluoroacetate (BFA), respectively: k1(EFA+OH) = (1.16 ± 0.61) by FTIR and (1.34 ± 0.62) by GC-FID; k2(ETB+OH) = (1.61 ± 0.90) by FTIR and (2.02 ± 0.77) by GC-FID; k3(BFA+OH) = (2.24 ± 0.96) by FTIR. Reactivity trends were developed and correlated with the number of CH3 and F substituents in the fluoroester, and structure-activity relationships (SARs) calculations were performed. In addition, the tropospheric lifetimes of EFA, ETB, and BFA upon degradation by OH radicals were calculated to be 9, 6, and 5 days, respectively, indicating that these fluorinated compounds could have a possible regional effect from the emission source. Relatively small photochemical ozone creation potentials of 9, 7, and 19 were estimated for EFA, ETB, and BFA, respectively. The global warming potentials (GWP) were: 1.393, 0.063 and 0.062 for a time horizon of 20 years, then for a time horizon of 100 years they were: 0.379, 0.017 and 0.017 and for a time horizon of 500 years they were: 0.108, 0.005 and 0.005 for EFA, ETB and BFA respectively. Being the EFA may contribute as a greenhouse gas, with the GWP(20yr) value of 1.393 being greater than GWPREF-CO2 = 1 (reference value).