Thermal Decomposition of Ethylbenzene, Styrene, and Bromophenylethane: UV Absorption Study in Shock Waves

Article abstract of DOI:10.1021/j100328a022

Shock wave studies of the pyrolysis of ethylbenzene, isopropylbenzene, tert-butylbenzene, styrene, and 1-bromo-1-phenylethane were performed using UV molecular absorption spectroscopy.By extensive spectral studies over the range 190-330 nm the overlapping absorption continua could be separated.Key observations in ethylbenzene pyrolysis were dominance of a primary C-C bond split, the comparably fast fragmentation of benzyl radicals in agreement with observations from other benzyl sources, and the evidence for nonnegligible styrene formation.The following rate constants were derived: ethylbenzene -> CH3 + benzyl, k₁ = 10^15.55 exp(-306.7 kJ mol^-1/RT) s^-1; styrene -> benzene + acetylene, k₁₅ = 10^11.2 exp(-244.5 kJ mol^-1/RT) s^-1; 1-bromo-1-phenylethane -> HBr + styrene, k₂₂ = 10^12.5 exp(-160 kJ mol^-1/RT) s^-1; benzyl fragmentation rates were identical with results from toluene, benzyl iodide, benzyl chloride, and other benzyl precursors.There is evidence for a dominant C-C bond split in isopropylbenzene and tert-butylbenzene pyrolysis as well.