Kinetics of the self-reactions of benzyl and o-xylyl radicals studied by cavity ring-down spectroscopy

The kinetics of the self-reactions of benzyl and o-xylyl radicals was studied experimentally over the temperature range 295–800 K. The radicals were produced by the 248-nm photolysis of oxalyl chloride followed by the H-abstraction reactions from toluene or o-xylene by Cl atoms and detected by cavity ring-down spectroscopy. The visible absorption cross sections of the radicals were determined relative to that of the HCO radical. The rate constants determined were k(benzyl + benzyl) = 1.29 × 10−3T−2.669exp(−674/T) cm3 molecule−1 s−1 (Δlog10k = ±0.096) and k(o-xylyl + o-xylyl) = 2.57T−3.784exp(−1025/T) cm3 molecule−1 s−1 (Δlog10k = ± 0.107).