Kinetics of abstraction reactions of methyl radicals with alkanes in gas phase

Abstract

Rate data for the abstraction reactions between methyl radicals and some alkanes viz. 2,2-dimethylpropane, 2,2,3,3-tetramethylbutane, cyclohexane, butane and 2-methylpropane (containing primary, secondary and tertiary C - H bonds) have been determined between 399 and 4.34K. The methyl radicals are generated by thermolysis of di-<em>t</em>-butyl peroxide. From the yields of methane and ethane, Arrhenius parameters for the reaction:<br /><br /> RH + CH3 → CH4 + R<br><br> have been obtained. They are log (A₆) = 7.93 ± 0.13, 7.95 ± 0.14, 8.07 ± 0.10, 7.96 ± 0.10 and 8.13 ± 0.20, and E₆/kJ mol^-1 = 47.59 ± 1.56, 46.17 ± 1.54, 40.14 ± 1.20, 38.94 ± 1.20 and 33.60 ± 2.30, respectively. The data obtained in this work are compared with those obtained by other workers. The experimentally determined activation energies for 2,2-dimethylpropane, cyclohexane, butane and 2-methylpropane are compared favourably with those calculated by a semiempirical method.