Isomer-selective study of the OH initiated oxidation of isoprene in the presence of O(2) and NO. I. The minor inner OH-addition channel.
- Additional Document Info
- View All
We report isomer-selective kinetics and mechanistic details for the hydroxyl radical-initiated oxidation of isoprene, in the presence of O(2) and NO, employing complementary experimental and theoretical techniques. Using a recently demonstrated photolytic route to initiate isomer-selective kinetics in OH-initiated oxidation of unsaturated hydrocarbons via the UV photolysis of iodohydrins, the photolysis of 1-iodo-2-methyl-3-buten-2-ol results in a single isomer of the possible four OH-isoprene adducts, specifically the minor channel associated with OH addition to one of the inner carbon atoms. Employing both the laser-photolysis/laser-induced fluorescence (LP/LIF) technique and time-dependent multiplexed photoionization mass spectrometry, we find clear experimental evidence supporting the prompt rearrangement of the initially formed beta-hydroxyalkyl radicals to alpha-hydroxyalkyl radicals, in agreement with Rice-Ramsperger-Kassel-Marcus (RRKM)/master equation predictions. We have determined a rate constant of (3.3 +/- 0.5) x 10(-11) cm(3) molecule(-1) s(-1) for molecular oxygen to abstract a hydrogen atom from the alpha-hydroxyalkyl radical to form 4-penten-2-one and HO(2). This reaction provides a mechanistic route to C(5) carbonyl species as first-generation end products for the addition of hydroxyl radical to isoprene in the presence of O(2) and NO.
author list (cited authors)
Greenwald, E. E., Ghosh, B., Anderson, K. C., Dooley, K. S., Zou, P., Selby, T., ... North, S. W.
complete list of authors
Greenwald, Erin E||Ghosh, Buddhadeb||Anderson, Katie C||Dooley, Kristin S||Zou, Peng||Selby, Talitha||Osborn, David L||Meloni, Giovanni||Taatjes, Craig A||Goulay, Fabien||North, Simon W