High Temperature Reactions of Benzyl Radicals

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Abstract
The thermal decomposition of benzyl radicals has been investigated behind reflected shock waves by monitoring the formation of hydrogen atoms. The results reported here have been obtained by using a shock tube in conjunction with atomic resonance absorption spectrometry (ARAS). The temperatures ranged between 1450 and 1700 K at total pressures around 2 bar. The test gas mixtures consisted of argon with relative concentrations of a few ppm benzyliodide, C7H7I. From the measurements of the temporal H‐atom concentrations, in connection with thermochemical restraints, it was deduced that the benzyl decay is preceded by isomerization of benzyl. Due to the low initial concentration of the radical precursor, it was possible to evaluate a first order rate coefficient for the initiation reaction: magnified image The heat of formation of the benzyl radical is discussed. A value of ΔH0f, 298 = 215.5 kJ mol−1 fits best to the experimental results.