Reaction of phenylperoxy radicals with NO2 at 298 K

Abstract

In the present work, phenylperoxy radicals were generated by stationary 254 nm photolysis of iodobenzene and nitrosobenzene in the presence of O₂ and NO₂ at 298 K and a total pressure of 1 bar (M = N₂). Experiments were performed on time scales of seconds or minutes in a temperature controlled photoreactor made of quartz (v = 209 L). Major gas phase products identified and quantified in situ by long-path IR absorption include N₂O₅, NO, HONO, HNO₃, CO, and o-nitrophenol. In addition, evidence is presented for the formation of an aerosol consisting of p-nitrophenol. The occurrence of N₂O₅ as a major product in both reaction systems, the strong loss of NO₂ in the iodobenzene system and the comparison of measured product distributions with the results of numerical model calculations suggest that the reactionoccurs in both photolysis systems, a major part of the NO₃ being scavenged as N₂O₅. The results of ab initio calculations imply that reaction (5) proceeds via a short-lived peroxynitrate intermediate. In the photolysis of nitrosobenzene–NO₂–O₂–N₂ mixtures, NO and NO₂ compete for C₆H₅O₂ radicals. Comparison of measured and modelled product distributions allows to set a lower limit of k₅ > 1 × 10⁻¹² cm³ molecule⁻¹ s⁻¹ at 298 K. This lower limit is consistent with the assumption that k₅ is equal to the high pressure recombination rate constant of RO₂ + NO₂ → RO₂NO₂ reactions, i.e. with