Gas phase oxidation of benzene: Kinetics, thermochemistry and mechanism of initial steps

Consecutive reactions of aromatic-OH adducts with NO, NO<sub>2</sub> and O<sub>2</sub>: benzene, naphthalene, toluene, m- and p-xylene, hexamethylbenzene, phenol, m-cresol and aniline

“…That ratio is much lower in our FP/RF experiments than in the experiments of Grebenkin and Krasnoperov (2004) and of Johnson et al (2002) and Raoult et al (2004) but even lower in the absorption experiments of our laboratory . In that experiment, however, an underlying background absorption with unknown formation kinetics has been subtracted, influencing the simultaneous determination of k 6 and the equilibrium constant (7/-7).…”

“…The formation of phenolics + HO 2 , favoured by Raoult et al (2004) to be direct rather than subsequent to Reaction (7), is not of that kind. Another loss process contributing to k 6 could be an unimolecular reaction in competition to Reaction (-7), e.g.…”

“…Another experiment less than a factor of 2 off the goal to detect a slow O 2 reaction is that of Perry et al (1977), who expressed their result on toluene-OH as being less than 1.0×10 −15 cm 3 s −1 at 353-397K. More recently, several authors studied the transient absorption of HCHD in the presence of O 2 , Johnson et al (2002), Raoult et al (2004), Grebenkin and Krasnoperov (2004)). provided first evidence of a fast equilibrium (7/-7) in the gas phase, predicted theoretically by Lay et al (1996) and Ghigo and Tonachini (1998) but already observed in water by Pan and Von Sonntag (1990).…”

“…Improvements of the apparatus of Johnson et al (2002) by Raoult et al (2004) allowed the use of lower radical concentrations which resulted in slower decays, corresponding to k 6 =2.5×10 −16 cm 3 s −1 . These discrepancies are obviously due to radical-radical reactions.…”

“…These aspects have been studied by laser photolysis/laser absorption and laser photolysis/UV absorption by Zellner et al (1985), , Bohn (2001), Johnson et al (2002Johnson et al ( , 2005, Raoult et al (2004) and Grebenkin and Krasnoperov (2004); by discharge-flow/laser induced fluorescence (Goumri et al, 1990); in flash photolysis/resonance fluorescence studies by Perry et al (1977), and Knispel et al (1990) for benzene, toluene and phenol; and in product studies by , Atkinson et al (1991), Atkinson and Aschmann (1994), Klotz et al (1998), Smith et al (1998, Bethel et al (2000), Berndt and Böge (2001a, 2001b, 2003 and Volkamer et al (2002a,b), Klotz et al (2002), Olariu et al (2002), Zhao et al (2005) and Coeur-Tourneur et al (2006) for benzene, toluene, o-, m-and p-xylene, 1,2,3-, 1,2,4-and 1,3,5-trimethylbenzene, HMB, phenol and o-, m-and p-cresol. In the following, we present a kinetic study of the consecutive reactions of aromatic-OH adducts in the presence of variable amounts of either NO, NO 2 or O 2 . Most of the results on benzene, toluene, p-xylene, phenol and m-cresol were obtained using the VUV flash photolysis/resonance fluorescence (FP/RF) technique, introduced by Stuhl and Niki (1972).…”