Direct investigations of reactions of 1-butoxy and 1-pentoxy radicals using laser pulse initiated oxidation: Reaction with O2 and isomerisation at 293 K and 50 mbar

Article abstract of DOI:10.1039/a903301g

The reactions of 1-butoxy and 1-pentoxy radicals were studied using time-resolved and simultaneous measurement of NO₂ and OH concentrations in laser pulse initiated oxidation studies followed by numerical simulations of the concentration profiles. The alkoxy radicals were produced selectively by the excimer-laser photolysis of 1-butyl bromide and 1-pentyl bromide at 248 nm and subsequent reaction of the 1-alkyl radicals with O₂ and NO. Whereas NO₂ was detected by cw-LIF, OH was monitored by laser long-path absorption at 308 nm. All experiments were performed at 293 ± 3 K and a total pressure of 50 mbar. The reactions with O₂ and the isomerisations via a 1,5-H-shift, viz., CH₃CH₂CH₂CH₂O + O₂ → CH₃CH₂CH₂CHO + HO₂ (5) CH₃CH₂CH₂CH₂O → CH₂CH₂CH₂CH₂OH (6) CH₃CH₂CH₂CH₂CH₂O + O₂ → CH₃CH₂CH₂CH₂CHO + HO₂ (25) CH₃CH₂CH₂CH₂CH₂O → CH₃CHCH₂CH₂CHOH (26) were investigated. Their rate coefficients were varied, utilizing the FACSIMILE integrator, until the best fits were obtained. Whereas in the case of 1- butoxy radicals absolute rate coefficients k(5) = (1.4 ⁺ 0.7) x 10^-14 cm³ molecule^-1 s^-1 and k₆ = (3.5 ± 2) x 10⁴ S^-1 could be derived, only limiting values for the 1-pentoxy radical reactions k₂₅ ≤ 1 X 10^{- 13} cm³ molecule^-1 s^-1 and k₂₆ ≥ 1.0 X 10⁵ S^-1 were obtained.