A kinetic study of the reactions of OH radicals with fluoroethanes. Estimates of C—H bond strengths in fluoroalkanes

Abstract

A kinetic study of the reactions of OH radicals with a series of fluoroethanes in the gas phase is presented. OH radicals were generated by flash photolysis of H₂O vapor in the vacuum uv (λ > 165 nm) and were monitored in absorption by time-resolved attenuation of resonance radiation at 308.15 nm [OH(A²Σ⁺ → X²Π)]. The following absolute rate constants (in units of 10⁹ cm³mol⁻¹ s⁻¹ at the 95% confidence limit) were determined at [Formula: see text][Formula: see text][Formula: see text][Formula: see text][Formula: see text]From a linear correlation of the present and previously published rate constants with bond dissociation energies, the following quantities (in kcal mol⁻¹ at 298 K) were estimated to be: D(CH₃CHF—H) = 96.3 ± 1.5, D(CH₂FCHF—H = 98.8 ± 1.0, D(CF₃CHF—H) = 103.5 ± 1.0, D(CHF₂CF₂—H) = 103.0 ± 1.5, and [Formula: see text][Formula: see text]