Shock-Tube Study of the Reactions of Hydrogen Atoms with Benzene and Phenyl Radicals

Abstract

Abstract The reactions of hydrogen atoms with phenyl radicals, H + C6H5 → products (1), and with benzene, H + C6H6 → products (2), have been studied behind reflected shock waves in the temperature range 1200–1350 K with argon as the bath gas. H-atom resonance absorption spectrometry at 121.6 nm was used as detection technique. Hydrogen atoms and phenyl radicals were produced by thermal decomposition of C2H5I and C6H5I, respectively. Low initial concentrations (~1012–1015 cm-3) were employed to suppress consecutive bimolecular reactions as far as possible.The rate coefficients were determined from fits of the H atom concentration-time profiles in terms of a small mechanism. For reaction (1), a temperature-independent rate coefficient k 1 = 1.3×10–10 cm3 s–1 was obtained at pressures around 1.3 bar. For the rate coefficient of reaction (2), the temperature dependence can be expressed as k 2(T) = 5.8×10–10 exp(–8107 K/T) cm3 s–1, and a pressure dependence was not observed between 1.3 and 4.3 bar. The uncertainties of k 1 and k 2 were estimated to be ±40%.