Thermal decomposition of benzyl radicals in shock waves

Abstract

The thermal decomposition of toluene has been used to prepare well defined concentrations of benzyl radicals in shock waves. The subsequent unimolecular dissociation of benzyl radicals has been investigated for the conditions 1550 ⩽T/K ⩽ 2020 and 1.4 × 10^–6⩽[Ar]/mol cm^–3⩽ 1.5 × 10^–4. The reaction was found to be in the fall-off range of the unimolecular reaction. A limiting high-pressure rate constant k_∞= 8.3 × 10¹⁷ exp (–455 kJ mol^–1/RT) s^–1 and a value for the benzyl dissociation energy at 0 K of ΔH^⊖₀= 430 ± 15 kJ mol^–1 have been derived.