Thermal Decomposition of Toluene: A Comparision of Thermal and Laser-Photochemical Activation Experiments

Article abstract of DOI:10.1021/j100328a021

The thermal decomposition of toluene has been reinvestigated in shock waves detecting toluene, benzyl radicals, and benzyl fragment concentrations by UV absorption spectroscopy in the range 190-320 nm.The experiments are interpreted in terms of a dominant toluene dissociation into benzyl radicals + H fragments with a rate constant k₁ = 10^{15.45 +/- 0.2} (exp(-(371.9 +/- 10) kJ mol^-1/RT) s^-1 (at = (2.6 +/- 0.4) * 10^-4 mol cm^-3) and in terms of a faster benzyl fragmentation which is in agreement with experiments on other benzyl sources.The derived thermally averaged rate constants of toluene dissociation k₁ are consistent with specific rate constants k(E,J) from laser excitation experiments.Similarly, the nature of the dominant product channel is consistently identified in thermal and photochemical experiments, ruling out a recently discussed dominance of fragmentation into the phenyl + methyl channel.