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The kinetics of the reaction between ethoxy (C2H5O) radicals and O2 have been studied using a combined laser photolysis/LIF technique for the generation and detection of C2H5O. In the temperature range 295–411 K the rate coefficient has been found to be . Product investigations using a chemical titration of HO2 by NO and subsequent quantitative detection of OH by LIF indicate the dominance of the HO2 formation channel, viz. with ϕ HO 2 = 0.89 (−0.12+0.22). Energy correlations show that these products are formed by a direct metathesis reaction only. It is suggested, that the low pre‐exponential factor in the Arrhenius expression may be the result of a more complex than linear configuration of the moiety in the transition state and/or of tunneling.

The absolute rate coefficients for the hydrogen abstraction reactions from CH 3 CCl 3 (k 1 ), CH 3 CCl 2 F (k 2 ), and CH 3 CClF 2 (k 3 ) by chlorine atoms in gas phase have been measured as a function of temperature using the discharge flow/mass spectrometric technique (DF/MS). The reactions were investigated under pseudo-firstorder conditions with Cl atoms in large excess with respect to the haloethanes. The temperature dependence of the rate coefficients is expressed in the Arrhenius form:) × 10 -12 exp-[-(2420 ( 400)/T]. The units of the rate constants are cm 3 molecule -1 s -1 , and the quoted uncertainties are (2σ. For understanding the reaction path mechanism of the chlorination of the studied halogen-substituted ethanes, ab initio molecular orbital calculations were performed. Transition state structures were determined. These calculations lead to predictions of preexponential factors in the same order of magnitude of measured values. The ab initio energetics of the reactions were corrected using the ISO-M method, a mixing of isodesmic reactions for obtaining reaction enthalpies and concept of intrinsic energy of Marcus to deduce activation energies. A reasonably good agreement with the experimental values were found.

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The rate coefficients for the hydrogen abstraction reactions from CHCl 3 (k 1 ), CHCl 2 F (k 2 ), and CHClF 2 (k 3 ) by chlorine atoms in the gas phase have been measured over the temperature range 298-430 K using the discharge flow/mass spectrometry technique (DF/MS) under pseudo-first-order conditions with Cl atoms in large excess with respect to the halomethane. The temperature dependence of the rate coefficients is expressed in the Arrhenius form:The units of the rate constants are cm 3 molecule -1 s -1 and the quoted uncertainties are 2σ. Wall loss and recombination of atomic chlorine (Cl + Cl + M) rate coefficients, k w and k r respectively, were measured and utilized in calculation of the rate coefficients. Inclusion of the Cl atom losses is shown to be important for the slower reactions requiring longer reaction times. Arrhenius expressions are in good agreement with available literature data and in very good agreement with recently reported theoretical (ab initio) calculations.