The reaction of trichloromethyl radicals with hydrogen chlorid and a new estimation of the rate of combination of trichloromethyl radicals

Abstract

The effect of the addition of hydrogen chloride on the photolysis of carbon tetrachloride in the presence of cyclohexane has been investigated in a companion paper. The data enable the rate constant ratio k8/(k5)1/2 to be determined. Since k−8 is well established, k5 can be estimated from known thermochemical data. The validity of the thermochemical derivation is checked by applying it to trifluoromethyl radicals. The photolysis of bromotrichloromethane and carbon tetrachloride in the presence of hydrogen chloride has been investigated over a range of temperatures. From these results and assuming reaction (5) has no activation energy, Arrhenius parameters for reaction (8) have been determined: The activation energies for the reaction of methyl, trichloromethyl, and trifluoromethyl radicals with hydrogen chloride are compared, and at first sight surprising results are rationalized in terms of relative electronegativity.

Kinetics and Mechanism of the Sonolytic Degradation of Chlorinated Hydrocarbons: Frequency Effects

“…This result indicates that the rate of the trichloromethyl radical self-reaction is clearly faster than the rate of • CCl 3 decomposition. Consistent with this argument is the fact that the rate constant for the self-reaction of the trichloromethyl radicals is to be 10 10 M -1 s -1 …”

“…Consistent with this argument is the fact that the rate constant for the self-reaction of the trichloromethyl radicals is to be 10 10 M -1 s -1 . 36 In a recent study, Kruus et al 6 reported on their observations of the reaction intermediates produced during the sonication of aqueous chloroform solutions at 900 kHz at an acoustic power of 25 W and an applied power density of 0.17 W cm -3 . With an initial concentration of [CHCl 3 ] o ) 4.2 mM, Kruus et al observed the formation of carbon tetrachloride (18 µM), tetrachloroethene (43 µM), hexachloroethane (32 µM), pentachloroethane (17 µM), trichloroethene (10 µM), 1,1,2,2tetrachloroethane (3 µM), and hexachlorobutadiene (4 µM) after 10 min of sonication.…”

Application of the Canonical Flexible Transition State Theory to CH3, CF3, and CCl3 Recombination Reactions

“…(c) CCl 3 + CCl 3 . The CCl 3 recombination reaction has been studied experimentally by several groups using indirect methods. − The first direct measurement was reported by Danis et al who observed the time-resolved decay of CCl 3 by UV absorption. They determined the recombination rate coefficients over a wide temperature range.…”

“…It was mainly chosen because of the availability of extensive experimental and theoretical data. − It also enables comparison of the results from this version of CFTST with the microcanonically and canonically derived rate coefficients for this recombination reaction by Wardlaw and Marcus . For the analogous halogenated systems (R2 and R3) there is, despite their importance, a substantial uncertainty in the experimentally determined rate coefficients, ,− especially for reaction R2. The main aim of the paper is to model the temperature dependence of the rate coefficients for three recombination reactions which are anticipated to become more sterically hindered as the reactants become bulkier.…”

The reaction of cyclopentyl radicals with carbon tetrachloride

“…(I) in Figure 1. Taking the rate constant for the combination of trichloromethyl radicals, k8 = L/mol-s, independent of temperature [12] we obtain a value of k6 = 108.4*0.4 exp[-(l0.0 f 0.7) kcal/mol/RT], which is in good agreement with that of Wampler and Kuntz [13], k6 = exp[-l0.7 kcal/mol/RT]. A few runs were carried out in which carbon tetrachloride was photolyzed in the presence of cyclopentane.…”