Abstract
The reactions of hydrogen atoms with phenyl radicals, H + C(6)H(5) -> products (1). and with benzene, H + C(6)H(6) -> 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 C(2)H(5)I and C(6)H(5)I, respectively. Low initial concentrations (similar to 10(12)-10(15) 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) = 1.3X10(-10) cm(3) 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) = 5.8X10(-10) exp(-8107 K/T) cm(3) 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%.