Single-Pulse Shock-Tube Studies on the Decomposition of 1,2-dibromoperfluoroethane and Allyl Bromide

Article abstract of DOI:10.1021/j150657a029

1,2-Dibromoperfluoroethane and allyl bromide have been decomposed in comparative rate single-pulse shock-tube experiments.Cyclopentane is used as a radical trap and as a source of the ethylene which serves as a direct measure of the number of radicals generated in the system.Under our reaction conditions both decomposition processes BrCF2CF2Br-->Br^. + C2F4Br^. (1) and allyl Br--> allyl + Br^. (2) are in the beginning of the falloff region, k/k_infinite >/= 0.7.RRKM calculations yield the following high-pressure rate expressions; k₁ = 1E15.2 exp(-32480/T)s^-1 and k₂ = 1E15.0 exp(-27540/T)s^-1.This leads to a bond dissociation energy for (BrCF2CF2-Br) = 278 kJ and ΔH_f(allyl, 298) = 173.6 kJ/mol.In combination with the thermodynamics, the recombination rate of allyl and bromine atom is found to be 1E14 cm³/(mol s) or collisional.The validity of such a general assumption is examined for the methyl bromide, allyl iodide, ethyl iodide, benzyl bromide, and benzyl chloride systems and appear to be in remarkable accord with experiments.