A kinetic study of the abstraction reactions of methyl radicals with cyclohexane and methyl-substituted cyclohexanes in the gas phase

Abstract EN

Rate constants and Arrhenius parameters corresponding to overall hydrogen abstraction by methyl radicals, generated by the pyrolysis of di-t-butyl peroxide, with cyclohcxane and a group of methyl-substituted cyclohexanes have been measured at several temperatures in the range of 373 - 433 K.

The determined rate data in this work are based on the value of (he rate constant for recombination of methyl radicals.

The overall rate constants for hydrogen abstraction by methyl radicals are expressed as the sum of contributions from each primary, secondary and tertiary hydrogen atom assuming the additivity principle for all of the following studied compounds: cyclohexane, methylcyclohexane, 1,1-dimethylcyclohexane, 1,3-dimethylculohexane, 1,2,4-Irimethylcyclohexane and 1,1.3-trimethylcyclohexane.

Using the additivity principle, it was possible to derive Arrhenius parameters for the secondary and tertiary hydrogen atoms, they are log(A/dmJ mol-1 s-') = 7.91 ± 0.15, 8.65 ± 0.23 and E/U mo"' - 38.1 ± 2.2, 34.9 ± 2.3, respectively.