Unraveling the structure and chemical mechanisms of highly oxygenated intermediates in oxidation of organic compounds

Wang, Zhandong; Popolan-Vaida, Denisia M.; Chen, Bingjie; Moshammer, Kai; Mohamed, Samah; Wang, Heng; Sioud, Salim; Raji, Misjudeen; Kohse‐Höinghaus, Katharina; Hansen, Nils; Dagaut, Philippe; Leone, Stephen R.; Sarathy, S. Mani

doi:10.1073/pnas.1707564114

Cited by 124 publications

(118 citation statements)

References 46 publications

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“…These resulting HO2PO2H radicals can react by third O2 addition reactions forming HO2P(O2)O2H radicals, and their subsequent reactions produce di-keto-hydroperoxides (DKHP, C8H14O5) and keto-di-hydroperoxides (KDHP, C8H16O6). Species with nominal masses corresponding to these peroxide species were experimentally detected as discussed earlier, supporting the proposed third O2 addition reactions, which is also consistent with recent studies by Wang and coworkers [39,40].…”

Section: Comparison Of Experiments and Modelssupporting

confidence: 91%

Probing the low-temperature chemistry of di-n-butyl ether: Detection of previously unobserved intermediates

Tran

Wullenkord

et al. 2019

Combustion and Flame

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Din -butyl ether (DBE, C8H18O) has been proposed as a promising biofuel for diesel engines, but details of its low-temperature (LT) oxidation chemistry are not well understood. This paper reports new speciation data obtained in the temperature range of 400-1100 K at ϕ=1 and nearly-atmospheric pressure, using a plug flow reactor (PFR) combined with electron ionization (EI) molecular-beam mass spectrometry (MBMS) and two different jet-stirred reactors (JSRs) coupled with either online gas chromatography (GC) or tunable synchrotron vacuum ultraviolet (SVUV) photoionization (PI)-MBMS. The experimental results confirm that DBE is very reactive and exhibits two negativetemperature coefficient (NTC) zones around 500-550 K and 650-750 K. Speciation data with about 40 C0-C8 species are presented, including about 20 LT species not reported previously. Among those, fuel-specific C8H16O2 cyclic ethers were quantified. Also, butanoic acid, which is present in highest amounts among the detected LT intermediates, and C8H14O3 diones, were found to peak already near 500 K, suggesting their importance in the LT chemistry of DBE. Signals of several highly oxygenated peroxides (e.g., C8H14O5 and C8H16O6) were detected, indicating third O2 addition steps. Respective reaction pathways are suggested and discussed based on these experimental results. To better understand the LT chemistry of DBE, the present data were compared to two recent DBE models [L. Cai et al. Combust. Flame. 161 (2014) 798-809 and S. Thion et al. Combust. Flame 185 (2017) 4-15]. Significant discrepancies between the experimental data and both models were found for important LT intermediates, of which many were not included in the respective mechanisms. The results reported in the present study thus provide new opportunities for refining DBE kinetic models.

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Section: Comparison Of Experiments and Modelssupporting

confidence: 91%

Probing the low-temperature chemistry of di-n-butyl ether: Detection of previously unobserved intermediates

Tran

Wullenkord

et al. 2019

Combustion and Flame

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“…alkanes [9,33,34,50], but they were observed in recent studies of 2-methylhexane [31], 2,5-dimethylhexane [30], and many other organic species [51]. In this work, the temperaturedependent signal profile of C7H14O5 ( Fig.…”

Section: C7h14ox Intermediates (X=0-5)mentioning

confidence: 51%

n-Heptane cool flame chemistry: Unraveling intermediate species measured in a stirred reactor and motored engine

Wang

Chen

Moshammer

et al. 2018

Combustion and Flame

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“…Subsequently, autoxidation was implicated in the generation of low-volatility molecules resulting from a single addition of OH or O 3 to monoterpenes (25)(26)(27)(28)(29)(30). In these systems, autoxidation reactions proceed through successive isomerizations and O 2 additions, resulting in the formation of molecules with high O/C ratios and, often, multiple hydroperoxide groups (31). Such compounds have recently been observed to undergo gas-particle transfer (32) and have been shown to be important in particle nucleation (33)(34)(35)(36)(37)(38)(39)(40)(41)(42)(43)(44)(45)(46)(47)(48)(49)(50).…”

mentioning

confidence: 99%

Atmospheric autoxidation is increasingly important in urban and suburban North America

Praske

Otkjær

Crounse

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

178

310

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Gas-phase autoxidation-regenerative peroxy radical formation following intramolecular hydrogen shifts-is known to be important in the combustion of organic materials. The relevance of this chemistry in the oxidation of organics in the atmosphere has received less attention due, in part, to the lack of kinetic data at relevant temperatures. Here, we combine computational and experimental approaches to investigate the rate of autoxidation for organic peroxy radicals (RO 2 ) produced in the oxidation of a prototypical atmospheric pollutant, n-hexane. We find that the reaction rate depends critically on the molecular configuration of the RO 2 radical undergoing hydrogen transfer (H-shift). RO 2 H-shift rate coefficients via transition states involving six-and seven-membered rings (1,5 and 1,6 H-shifts, respectively) of α-OH hydrogens (HOC-H) formed in this system are of order 0.1 s −1 at 296 K, while the 1,4 H-shift is calculated to be orders of magnitude slower. Consistent with H-shift reactions over a substantial energetic barrier, we find that the rate coefficients of these reactions increase rapidly with temperature and exhibit a large, primary, kinetic isotope effect. The observed H-shift rate coefficients are sufficiently fast that, as a result of ongoing NO x emission reductions, autoxidation is now competing with bimolecular chemistry even in the most polluted North American cities, particularly during summer afternoons when NO levels are low and temperatures are elevated.atmospheric chemistry | air pollution | autoxidation

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Unraveling the structure and chemical mechanisms of highly oxygenated intermediates in oxidation of organic compounds

Cited by 124 publications

References 46 publications

Probing the low-temperature chemistry of di-n-butyl ether: Detection of previously unobserved intermediates

Probing the low-temperature chemistry of di-n-butyl ether: Detection of previously unobserved intermediates

n-Heptane cool flame chemistry: Unraveling intermediate species measured in a stirred reactor and motored engine

Atmospheric autoxidation is increasingly important in urban and suburban North America

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