Absolute and relative-rate measurement of the rate coefficient for reaction of perfluoro ethyl vinyl ether (C2F5OCFCF2) with OH

Abstract

The rate coefficient (k₁) for the reaction of OH radicals with perfluoro ethyl vinyl ether (PEVE, C₂F₅OCFCF₂) has been measured as a function of temperature (T = 207–300 K) using the technique of pulsed laser photolysis with detection of OH by laser-induced fluorescence (PLP-LIF) at pressures of 50 or 100 Torr N₂ bath gas. In addition, the rate coefficient was measured at 298 K and in one atmosphere of air by the relative-rate technique with loss of PEVE and reference reactant monitored in situ by IR absorption spectroscopy. The rate coefficient has a negative temperature dependence which can be parameterized as: k₁(T) = 6.0 × 10⁻¹³ exp[(480 ± 38/T)] cm³ molecule⁻¹ s⁻¹ and a room temperature value of k₁ (298 K) = (3.0 ± 0.3) × 10⁻¹² cm³ molecule⁻¹ s⁻¹. Highly accurate rate coefficients from the PLP-LIF experiments were achieved by optical on-line measurements of PEVE and by performing the measurements at two different apparatuses. The large rate coefficient and the temperature dependence indicate that the reaction proceeds via OH addition to the CC double bond, the high pressure limit already being reached at 50 Torr N₂. Based on the rate coefficient and average OH levels, the atmospheric lifetime of PEVE was estimated to be a few days.