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

• Published in: Journal of environmental sciences (China) 2025-05, Vol.151, p.273-283
• Main Authors: Lugo, Pedro L., Straccia, Vianni, Teruel, Mariano A., Blanco, María B.
• Format: Article
• Language: English
• Subjects: Acidification potentials; Air Pollutants - analysis; Air Pollutants - chemistry; Butyrates - chemistry; CFC replacements sinks; Fluoroacetates; Greenhouse gases; Hydroxyl Radical - chemistry; in situ FTIR; Kinetics; Models, Chemical; SAR
• ISSN: 1001-0742
• DOI: 10.1016/j.jes.2024.02.026

•Agreement between in situ FTIR and GC-FID measurements and SAR calculations.•Reactivity of FES with OH increases with H and decreases with F substitution.•The greatest probability of abstraction of H atoms occurs in the secondary carbons (CH2).•Ethyl 4,4,4-trifluorobutyrate could be involved in acid rain events with AP of 0.56.•Ethyl fluoroacetate candidate of greenhouse gas with GWP of 1.66. 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 cm3/(molecule•sec)) were obtained for ethyl fluoroacetate (EFA), ethyl 4,4,4-trifluorobutyrate (ETB), and butyl fluoroacetate (BFA), respectively: k1 (EFA + OH) = 1.15 ± 0.25 by FTIR and 1.34 ± 0.23 by GC-FID; k2 (ETB + OH) = 1.61 ± 0.36 by FTIR and 2.02 ± 0.30 by GC-FID; k3 (BFA + OH) = 2.24 ± 0.37 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 (GWPs) for EFA, ETB, and BFA were calculated for different time horizons. For a 20-year time horizon, the GWPs were 1.393, 0.063, and 0.062, respectively. In the case of a 100-year time horizon, the GWPs were 0.379, 0.017, and 0.017, and for a 500-year time horizon, the GWPs were 0.108, 0.005, and 0.005 for EFA, ETB, and BFA.