Kinetics of the reactions of OH(X2Π) radicals with 1,3-dioxolane and selected dialkoxy methanes

Abstract

The gas-phase reaction of OH(X²Π) radicals with 1,3-dioxolane was investigated in the temperature range 250–550 K. The reactions of OH(X ²Π) with di-isopropoxy methane (DiPM), di-n-butoxy methane (DnBM) and di-sec-butoxy methane (DsBM) were studied below room temperature down to 250 K. The experiments were carried out in argon, mostly at a total pressure of 400 Torr. A few additional measurements for the reaction OH + 1,3-dioxolane at 50 Torr exhibited that this reaction is independent of total pressure in the range investigated. OH radicals were generated by excimer laser photolysis of H₂O₂ and were detected by laser-induced fluorescence. For the OH + 1,3-dioxolane reaction, no temperature dependence was observed within the experimental errors. The bimolecular rate coefficient is well described by k_OH+dioxolane(T) = (8.2 ± 1.3) × 10⁻¹² cm³ s⁻¹. The rate coefficients measured for the reactions of OH with DiPM, DnBM and DsBM are discussed together with literature data obtained for higher temperatures. The Arrhenius plots for each reaction exhibited concave upward curvatures. From these data, the following Arrhenius expressions were derived (with T in K and E₀ in kJ mol⁻¹):

The given expressions for the rate coefficients are only valid within the limited temperature range of the present experiments. Since the equations are not theoretically supported, an extrapolation to other temperatures is not allowed.