Degradation of a series of fluorinated acrylates and methacrylates initiated by OH radicals at different temperatures

Abstract

Rate coefficients for the gas-phase reactions of OH radicals with a series of fluorinated acrylates and methacrylates: 2,2,2-trifluoroethylmethacrylate (k₁), 1,1,1,3,3,3-hexafluoroisopropylacrylate (k₂), 1,1,1,3,3,3-hexafluoroisopropylmethacrylate (k₃), and 2,2,2-trifluoroethylacrylate (k₄) have been measured for the first time as a function of temperature in the range 290–308 K. The kinetic data obtained were used to derive the following Arrhenius expressions (in units of cm³ per molecule per s): k₁ = (2.13 ± 0.68) × 10⁻¹⁸ exp[(4745 ± 206)/T], k₂ = (8.72 ± 0.68) × 10⁻¹⁵ exp[(2166 ± 205)/T], k₃ = (6.30 ± 0.51) × 10⁻¹⁷ exp[(3721 ± 153)/T] and k₄ = (3.93 ± 0.43) × 10⁻¹⁶ exp[(3140 ± 129)/T]. The experiments were performed at normal atmospheric pressure in synthetic air using a 1080 L photoreactor and coupled with FTIR analysis to monitor the decay of the substances of interest and the reference compounds. The obtained negative temperature dependencies are in agreement with a mechanism implying an initial addition of the OH radical to the double bond. Atmospheric implications are discussed with reference to the rate coefficients obtained as a function of the temperature.