Rate constants for abstraction of hydrogen from benzene, toluene, and cyclopentane by methyl and ethyl radicals over the temperature range 650–770 K

Abstract

. Can. J. Chem. 67, 1541 (1989). Rate constants for the abstraction of hydrogen from benzene, toluene, and cyclopentane by methyl and ethyl radicals have been measured relative to the corresponding abstraction reaction from ethylene. The method is based on the effect on the rates of formation of methane and ethane of the addition of small quantities of the reactants to the thermal chain reactions of ethylene in the temperature range 650-770 K. Taking the following values of the rate constants for the reference reactions (R = 8.314 J mol-' K-I):[4] C2Hs + C2H4 -* C2H6 + C2H3; log k4 (L mol-' s-I) = 8.2 t-0.2 -(62200 t-3000)/2.3RT the following rate constants were measured:[8] C2Hs + C6H6 -* C2H6 + C6HS; log kg (~m 0 1 -' S-') = 8.8 i 0.3 -(62200 i 5000)/2.3RT [ l l ] CH3 + C7Hg + CH4 + C7H7; log kll (L mol-' s-') = 7.4 i 0.5 -(29000 ? 7000)/2.3RT[12] C2HS + C7H8 'C2H6 + C7H7; log k12 ( L m~l -' s -~) = 7.7 * 0.5 -(37000 ? 7000)/2.3RT[15] CH3 + c-CsHlo -CH4 + c-C5Hg; log klS (L mol-' s-I) = 8.3 2 0.5 * (36000 ?7000)/2.3RTThe values of the activation energies are discussed in relation to the dissociation energies of the C-H bonds in the reactants.

Kinetics of the Hydrogen Abstraction •CH3 + Alkane → CH4 + Alkyl Reaction Class: An Application of the Reaction Class Transition State Theory

“…C 2 H 6 . Experimental reaction rates for those cyclic systems were previously reported in a number of studies [51][52][53]. Figure 7a-f shows the predicted rate constants of these reactions using the RC-TST method and from the literature data.…”

“…for reactions (a, b), ref [50]. for reactions (c, d), ref [51][52][53] for reaction (e), and ref [53] for reaction (f) whereas in this study, we employed the M062X functional which is known to be more accurate for kinetics. Within the RC-TST framework, the potential energy factor is the most sensitive to the choice of the DFT functional and thus is used to address this issue here.…”

The homogeneous thermal conversion of methane to higher hydrocarbons in the presence of ethylene

“…As a first approximation we assume that the concentration of ethyl radicals is unchanged in the presence of methane and given, as before, by eq. [17]. Under these conditions the rate of formation of butene-1 will be unchanged, as expressed by eq.…”

A DFT‐Based Investigation of Hydrogen Abstraction Reactions from Methylated Polycyclic Aromatic Hydrocarbons

“…The only available experimental information is known for toluene: for hydrogen abstraction by means of a methyl radical seven experimental data sets are available. [61][62][63][64][65][66][67] The experiments have been performed under various temperature conditions that vary from 373 to 983 K. Hence, the derived kinetic parameters can differ substantially depending on the temperature range, which in some cases is very small. The temperature intervals and the corresponding kinetic parameters of the various experiments are given in Table 2.…”

“…[60] Unfortunately, very little information is available on the experimental side, except for the hydrogen abstraction reaction at toluene using a methyl radical for which at least seven experiments report relevant data. [61][62][63][64][65][66][67] The experiments were performed under various temperature conditions, which varied from 373 to 983 K. The derived kinetic parameters can differ substantially and in some cases the small temperature range generates large errors in the extraction of the kinetic parameters. We will hence focus on the direct comparison of rate constants as we have done earlier.…”