On the similarities and differences between the products of oxidation of hydrocarbons under simulated atmospheric conditions and cool flames

Abstract. Atmospheric oxidation chemistry and, more specifically, photooxidation show that the long-term of organic aerosol (OA) progressively erases initial signature chemical compounds and can lead to a relatively uniform character oxygenated (OOA). This uniformity observed after long reaction time seems contrast with great diversity mechanisms in early stages oxidation. The numerous studies carried out on terpenes, particularly limonene for its sites (endo- oxocyclic), allow this evolution be studied. We have selected, their experimental conditions, nine at room temperature over times compared present data set obtained elevated short order investigate similarities terms species formed. Here, limonene–oxygen–nitrogen mixtures was studied using jet-stirred reactor atmospheric pressure. Samples reacting were collected analyzed by high-resolution mass spectrometry (Orbitrap) direct injection or separation reverse-phase ultra-high-pressure liquid chromatography soft ionization, i.e., (+/-) HESI APCI. Unexpectedly, because conditions continuous-flow tank reactor, concentration reactants, temperature, time, techniques, analysis results indicate among 1138 presently detected molecular formulae, many oxygenates found earlier OH and/or ozone are also produced under conditions. Among these highly molecules oligomers work. discussed pathways involving formation peroxy radicals (RO2), isomerization reactions yielding keto-hydroperoxides, other intermediates products up C25H32O17, which could derive from RO2 autoxidation via sequential H shift O2 addition (C10H14O3,5,7,9,11) deriving alkoxy (produced self-reaction HO2) through multiple shifts additions (C10H14O2,4,6,8,10). RO2, possible occurrence Waddington mechanism Korcek mechanism, is discussed. work demonstrates similitude between simulated those encountered during self-ignition hydrocarbons temperatures. These complement recently reported Vereecken Nozière confirm existence an oxidative alkylperoxy radical beyond 450 K based (Nozière Vereecken, 2019; Nozière, 2020).