Hydrogen abstraction from toluene by methyl radicals and the pressure dependence of the recombination of methyl radicals

Abstract

Using dimethylzinc, dimethylmercury, and trimethylbismuth as sources of methyl radicals, values of k 1 /k 2 1/2 [Formula: see text]have been calculated from 338 to 610 °C over the pressure range 4.5–204 mm. M is predominantly toluene. The observed pressure dependence of reaction [2] is in agreement with that found when M = benzene, but is somewhat greater, and the fall-off occurs at higher pressures, than for ethane dissociation. However, reasonable agreement is obtained if it is assumed that the efficiency of toluene as a third body in reaction [2] is about 1/10th that of ethane.Extrapolation to infinite pressure, where it is assumed that E 2 = 0and A 2 = 10 13.34 cm 3 mole −1 s −1 , gives E 1 = 8.0 ± 0.3 kcal mole −1 and A 1 = 10 11.07 cm 3 mole −1 s −1 .