Absolute Reaction Rates of Chlorine Atoms with CF₃CH₂OH, CHF₂CH₂OH, and CH₂FCH₂OH

Abstract

The absolute rate constants for the reactions of chlorine atoms with a series of fluorinated ethanols CF3CH2OH (1), CHF2CH2OH (2), and CH2FCH2OH (3) were measured in the gas phase over the temperature range 273−363 K, by employing the discharge-flow mass spectrometric technique with a Knudsen type reactor. The absolute rate constants are given by the following expressions (in cm3 molecule-1 s-1, 2σ uncertainties): k1 = (0.85 ± 0.19) × 10-11 exp((−792 ± 74)/T), k2 = (2.61 ± 0.49) × 10-11 exp((−662 ± 60)/T), and k3 = (7.57 ± 0.98) × 10-11 exp((−408 ± 40)/T). The title reactions take place primarily via the abstraction of methylene hydrogen, yielding the corresponding fluoroethanol radicals, which subsequently may undergo oxidation reactions, resulting in fluoroacetaldehydes. Quantum mechanical calculations of the C−H bond energies in the title alcohols at the B3P86/6-311++G(2df,p) level of theory show that the methylene hydrogen bonds are the weakest. The atmospheric degradation mechanism of the title fluorinated ethanols is also presented.