Rate Coefficients of the Reactions of Chlorine Atoms with Haloethanes of Type CH₃CCl_3-xF_x(x= 0, 1, and 2):  Experimental and ab Initio Theoretical Studies

Abstract

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.

Environmental effects of large igneous province magmatism: a Siberian perspective

“…Cl + CH 3 CCl 3 . The recommended value for k(298 K) is an average of the results from the absolute rate study by Talhaoui et al [1279] and the relative rate study by Platz et al [1063]. The recommended value for E/R is derived from a fit to the data of Talhaoui et al It is reasonably consistent with the value derived by Cillien et al [267] in a relative rate study conducted over a very narrow temperature range above room temperature, but is somewhat smaller than the value derived in the relative rate study of Tschuikow-Roux et al [1324].…”

“…Cl + CH 3 CF 2 Cl (HCFC-142b). The recommended value for k(298 K) is an average of the results of the relative rate studies of Wallington and Hurley [1404], and Tuazon et al [1326], and the absolute rate studies of Jourdain et al [682] and Talhaoui et al [1279], which is assumed to supercede the earlier study by Sawerysyn et al [1151]. The recommended temperature dependence is a fit to the data of Talhaoui et al The A-factor from that study has been adjusted to fit the recommended room temperature value.…”

Pyrolysis of 1,1-dichloro-1-fluoroethane in the absence and presence of added propene or CCl4: A computer-aided kinetic study

“…The value for the preexponential factor and the rate constant is estimated at 10 9.3 L/mol.s [9]. e Experimental value from [10]. f Assumed to be equal to the value for from [11], derived from fitting to a mechanism.…”

“…For the sake of completeness, numerical calculations show that (i) the reactions (5), (6), (10), and (12) tend rapidly towards a steady state of quasiequilibrium; (ii) the amounts of the side products Cl 2 , CHClFCH 3 , CCl 3 H, and C 2 Cl 6 formed in steps (10) to (13), respectively, are at least 10 3 times lower than that of the reaction product CClF " CH 2 ; and (iii) CCl 4 is almost not consumed in the course of the reaction.…”

Kinetics of the gas‐phase reactions of chlorine atoms with CH2F2, CH3CCl3, and CF3CFH2 over the temperature range 253–553 K

“…Measurements of k(Cl + CH 2 F 2 ) at 298 K by Tschuikow-Roux et al [3] and Nielsen et al [4] differ by a factor of 2, and the work by TschuikowRoux et al [3] provides the only information concerning the temperature dependence of the reaction. Measurements of k(Cl + CH 3 CCl 3 ) at 280-418 K by Cillien et al [5], Tschuikow-Roux et al [6], Platz et al [7], and Talhaoui et al [8] span a range of approximately 2. Measurements of k(Cl + CF 3 CFH 2 ) at 298 K by Sawerysyn et al [9], Wallington and Hurley [10], Tuazon et al [11], Louis et al [12], and Kaiser [13] are in excellent agreement; however, only limited data are available at temperatures below ambient.…”