作者: A. W. H. Chan , M. N. Chan , J. D. Surratt , P. S. Chhabra , C. L. Loza
关键词: Organic chemistry 、 Isoprene 、 Hydrocarbon 、 Methyl group 、 Aldehyde 、 Photochemistry 、 Acrolein 、 Crotonaldehyde 、 Methacrolein 、 Chemistry 、 NOx
摘要: Abstract. Aldehydes are an important class of products from atmospheric oxidation hydrocarbons. Isoprene (2-methyl-1,3-butadiene), the most abundantly emitted non-methane hydrocarbon, produces a significant amount secondary organic aerosol (SOA) via methacrolein (a C4-unsaturated aldehyde) under urban high-NOx conditions. Previously, we have identified peroxy methacryloyl nitrate (MPAN) as intermediate to isoprene and SOA in this NOx regime. Here show that result chemistry, NO2 enhances formation two other α, β-unsaturated aldehydes, specifically acrolein crotonaldehyde, effect on previously unrecognized. Oligoesters dihydroxycarboxylic acids hydroxynitrooxycarboxylic observed increase with increasing NO2/NO ratio, previous characterizations confirmed by both online offline high-resolution mass spectrometry techniques. Molecular structure also determines formation, yields highest for aldehydes contain additional methyl group α-carbon. Aerosol 2-methyl-3-buten-2-ol (MBO232) is insignificant, even high-NO2 conditions, PAN (peroxy acyl nitrate, RC(O)OONO2) structurally unfavorable. At atmospherically relevant ratios (3–8), photooxidation 3 times greater than measured at lower ratios. sufficiently high concentrations, systems subsequent peroxyl radicals+NO2 can exceed RO2+HO2 reactions same inorganic seed making RO2+NO2 channel formation.