Products and mechanism of the reaction of OH radicals with 2,3,4-trimethylpentane in the presence of NO.
Alkanes are important constituents of gasoline fuel and vehicle exhaust, with branched alkanes comprising a significant fraction of the total alkanes observed in urban areas. Using a relative rate method, a rate constant for the reaction of OH radicals with 2,3,4-trimethylpentane of (6.84+/-0.12) x 10(-12) cm3 molecule(-1) s(-1) at 298+/-2 K was measured, where the indicated error is two least-squares standard deviations and does not include the uncertainty in the rate constant for the n-octane reference compound. Products of the gas-phase reaction of OH radicals with 2,3,4-trimethylpentane in the presence of NO at 298+/-2 K and atmospheric pressure of air have been investigated using gas chromatography with flame ionization detection (GC-FID), combined gas chromatographymass spectrometry (GC-MS), and in situ atmospheric pressure ionization tandem mass spectrometry (API-MS). Products identified and quantified by GC-FID and GC-MS were (molar yields given in parentheses): acetaldehyde (47+/-6%), acetone (76+/-11%), 3-methyl-2-butanone (41+/-5%), 3-methyl-2-butyl nitrate (1.6+/-0.2%), and 2-propyl nitrate (6.2+/-0.8%). These compounds account for 69+/-6% of the reaction products, as carbon. Additional products observed by API-MS analyses using positive and negative ion modes were C5- and C8-hydroxynitrates and a C8-hydroxycarbonyl, which, together with the predicted formation of octyl nitrates, account for some or all of the remaining products. The product distribution is compared to those for the linear and branched C8-alkanes n-octane and 2,2,4-trimethylpentane.
Aschmann
Sara M
SM
Air Pollution Research Center, University of California, Riverside, California 92521, USA.
Arey
Janet
J
Atkinson
Roger
R
D000393:Air Pollutants; D017665:Hydroxyl Radical / Q000737:chemistry*; D008956:Models, Chemical; D009569:Nitric Oxide / Q000737:chemistry; D016877:Oxidants / Q000737:chemistry*; D010420:Pentanes / Q000737:chemistry*; D001335:Vehicle Emissions
D000393:Air Pollutants; D016877:Oxidants; D010420:Pentanes; D001335:Vehicle Emissions; D009569:Nitric Oxide; D017665:Hydroxyl Radical; C053045:2,3,4-trimethylpentane