Molecular mechanism for rapid autoxidation in α-pinene ozonolysis

Nature Communications, Journal Year: 2021, Volume and Issue: 12(1)

Published: Feb. 9, 2021

Aerosol affects Earth's climate and the health of its inhabitants. A major contributor to aerosol formation is oxidation volatile organic compounds. Monoterpenes are an important class compounds, recent research demonstrate that they can be converted low-volatility precursors on sub-second timescales following a single oxidant attack. The α-pinene + O3 system particularly efficient in this regard. However, actual mechanism behind conversion not understood. key challenge steric strain created by cyclobutyl ring products. This hinders subsequent unimolecular hydrogen-shift reactions essential for lowering volatility. Using quantum chemical calculations targeted experiments, we show excess energy from initial ozonolysis reaction lead novel intermediates without strain, allowing rapid products with up 8 oxygen atoms. likely route atmospheric formation.

Language: Английский

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Molecular composition and volatility of multi-generation products formed from isoprene oxidation by nitrate radical

Atmospheric chemistry and physics, Journal Year: 2021, Volume and Issue: 21(13), P. 10799 - 10824

Published: July 16, 2021

Abstract. Isoprene oxidation by nitrate radical (NO3) is a potentially important source of secondary organic aerosol (SOA). It suggested that the second or later-generation products are more substantial contributors to SOA. However, there few studies investigating multi-generation chemistry isoprene-NO3 reaction, and information about volatility different isoprene nitrates, which essential evaluate their potential form SOA determine atmospheric fate, rare. In this work, we studied reaction between NO3 in SAPHIR chamber (Jülich) under near-atmospheric conditions. Various were measured high-resolution time-of-flight chemical ionization mass spectrometer using Br− as reagent ion. Most detected they grouped into monomers (C4 C5 products) dimers (C10 with 1–3 groups according composition. observed match expected termination previous studies, but some compounds such three nitrogen atoms rarely reported literature gas-phase from NO3. Possible formation mechanisms for these proposed. The characterized taking advantage time behavior products. addition, vapor pressures diverse nitrates calculated parametrization methods. An estimation pressure also derived condensation behavior. According our results, belong intermediate-volatility semi-volatile thus have little effect on formation. contrast, low extremely volatility, indicating constitute 80 % total explained signals average, while contribute less than 2 %, suggesting contribution should be We expect yield 5 wall-loss- dilution-corrected concentrations, assuming all low- low-volatility compound (LVOC ELVOC) range will condense completely.

Language: Английский

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Highly Oxygenated Organic Nitrates Formed from NO₃ Radical-Initiated Oxidation of β-Pinene

Environmental Science & Technology, Journal Year: 2021, Volume and Issue: 55(23), P. 15658 - 15671

Published: Nov. 22, 2021

The reactions of biogenic volatile organic compounds (BVOC) with the nitrate radicals (NO3) are major night-time sources nitrates and secondary aerosols (SOA) in regions influenced by BVOC anthropogenic emissions. In this study, formation gas-phase highly oxygenated molecules-organic (HOM-ON) from NO3-initiated oxidation a representative monoterpene, β-pinene, was investigated SAPHIR chamber (Simulation Atmosphere PHotochemistry large Reaction chamber). Six monomer (C = 7–10, N 1–2, O 6–16) five accretion product 17–20, 2–4, 9–22) families were identified further classified into first- or second-generation products based on their temporal behavior. time lag observed peak concentrations between peroxy containing odd even number oxygen atoms, as well corresponding termination products, provided constraints HOM-ON mechanism. can be explained unimolecular bimolecular radicals. A dominant portion carbonylnitrates detected, highlighting significance intramolecular H-shift for HOM-ON. mean molar yield estimated to 4.8% (−2.6%/+5.6%), suggesting significant contributions SOA formation.

Language: Английский

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Efficient alkane oxidation under combustion engine and atmospheric conditions

Communications Chemistry, Journal Year: 2021, Volume and Issue: 4(1)

Published: Feb. 18, 2021

Abstract Oxidation chemistry controls both combustion processes and the atmospheric transformation of volatile emissions. In engines, radical species undergo isomerization reactions that allow fast addition O 2 . This chain reaction, termed autoxidation, is enabled by high engine temperatures, but has recently been also identified as an important source for highly oxygenated in atmosphere, forming organic aerosol. Conventional knowledge suggests autoxidation requires suitable structural features, like double bonds or oxygen-containing moieties, precursors. With neither these functionalities, alkanes, primary fuel type engines class urban trace gases, are thought to have minor susceptibility extensive autoxidation. Here, utilizing state-of-the-art mass spectrometry, measuring radicals oxidation products, we show alkanes much more efficiently than previously thought, under conditions. Even at concentrations NO X , which typically rapidly terminates areas, studied C 6 –C 10 produce considerable amounts products can contribute The results this inter-disciplinary effort provide crucial information on with direct implications efficiency air quality.

Language: Английский

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Structures and reactivity of peroxy radicals and dimeric products revealed by online tandem mass spectrometry

Nature Communications, Journal Year: 2021, Volume and Issue: 12(1)

Published: Jan. 12, 2021

Abstract Organic peroxy radicals (RO 2 ) play a pivotal role in the degradation of hydrocarbons. The autoxidation atmospheric RO produces highly oxygenated organic molecules (HOMs), including low-volatility ROOR dimers formed by bimolecular + reactions. HOMs can initiate and greatly contribute to formation growth particles. As result, have far-reaching health climate implications. Nevertheless, structures mechanism remain elusive. Here, we present in-situ characterization dimer structure gas-phase, using online tandem mass spectrometry analyses. In this study, constrain pathway several HOM-RO produced from monoterpene ozonolysis, prominent oxidation process. addition providing insights into HOM chemistry, study debuts MS analyses as unique approach for chemical reactive compounds, e.g., radicals.

Language: Английский

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Highly oxygenated organic molecule (HOM) formation in the isoprene oxidation by NO<sub>3</sub> radical

Atmospheric chemistry and physics, Journal Year: 2021, Volume and Issue: 21(12), P. 9681 - 9704

Published: June 29, 2021

Abstract. Highly oxygenated organic molecules (HOM) are found to play an important role in the formation and growth of secondary aerosol (SOA). SOA is type with significant impact on air quality climate. Compared oxidation volatile compounds by ozone (O3) hydroxyl radical (OH), HOM nitrate (NO3), oxidant at nighttime dawn, has received less attention. In this study, reaction isoprene NO3 was investigated SAPHIR chamber (Simulation Atmospheric PHotochemistry a large Reaction chamber). A number HOM, including monomers (C5), dimers (C10), trimers (C15), both closed-shell open-shell peroxy radicals (RO2), were identified classified into various series according their formula. Their pathways proposed based observed known mechanisms literature, which further constrained time profiles after sequential addition differentiate first- second-generation products. containing one three N atoms (1–3N-monomers) formed, starting carbon double bond, forming radicals, followed autoxidation. 1N-monomers formed direct first-generation 2N-monomers (e.g., C5H8N2On(n=7–13), C5H10N2On(n=8–14)) likely termination products C5H9N2On⚫, C5-hydroxynitrate (C5H9NO4), product bond. 2N-monomers, products, dominated accounted for ∼34 % all indicating + under our experimental conditions. H shift alkoxy form subsequent autoxidation (“alkoxy–peroxy” pathway) be pathway formation. mostly accretion monomer RO2 via reactions dimer possibly C5–RO2 isoprene. RO2. The concentrations different showed distinct during reaction, linked pathway. either typical profile or combination both, multiple and/or isomers. Total molar yield estimated 1.2 %-0.7%+1.3%, corresponded ∼3.6 assuming molecular weight C5H9NO6 as lower limit. This suggests that may contribute fraction NO3.

Language: Английский

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Theoretical and experimental study of peroxy and alkoxy radicals in the NO₃-initiated oxidation of isoprene

Physical Chemistry Chemical Physics, Journal Year: 2021, Volume and Issue: 23(9), P. 5496 - 5515

Published: Jan. 1, 2021

Under atmospheric conditions, nitrate-RO₂ radicals are equilibrated and react predominantly with HO₂, RO₂ NO. The nitrate-RO chemistry is affected strongly by ring closure to epoxy radicals, impeding formation of MVK/MACR.

Language: Английский

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Efficient Production of Carbonyl Sulfide in the Low‐NO_x Oxidation of Dimethyl Sulfide

Geophysical Research Letters, Journal Year: 2022, Volume and Issue: 49(3)

Published: Jan. 20, 2022

Abstract The oxidation of carbonyl sulfide (OCS) is the primary, continuous source stratospheric sulfate aerosol particles, which can scatter shortwave radiation and catalyze heterogeneous reactions in stratosphere. While it has been estimated that dimethyl (DMS), emitted from surface ocean accounts for 8%–20% global OCS source, there no existing DMS mechanism relevant to marine atmosphere consistent with an this magnitude. We describe new laboratory measurements theoretical analyses provide a mechanistic description production hydroperoxymethyl thioformate, ubiquitous, soluble product. incorporate chemical into transport model, showing factor 3 smaller than current estimates, displays maximum tropics field observations sensitive multiphase cloud chemistry.

Language: Английский

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Linking gas, particulate, and toxic endpoints to air emissions in the Community Regional Atmospheric Chemistry Multiphase Mechanism (CRACMM)

Atmospheric chemistry and physics, Journal Year: 2023, Volume and Issue: 23(9), P. 5043 - 5099

Published: May 4, 2023

Abstract. Chemical mechanisms describe the atmospheric transformations of organic and inorganic species connect air emissions to secondary such as ozone, fine particles, hazardous pollutants (HAPs) like formaldehyde. Recent advances in our understanding several chemical systems shifts drivers chemistry warrant updates used transport models Community Multiscale Air Quality (CMAQ) modeling system. This work builds on Regional Atmospheric Chemistry Mechanism version 2 (RACM2) develops Multiphase (CRACMM) 1.0, which demonstrates a fully coupled representation leading ozone aerosol (SOA) with consideration HAPs. CRACMMv1.0 includes 178 gas-phase species, 51 particulate 508 reactions spanning heterogeneous pathways. To support estimation health risks associated HAPs, nine CRACMM cover 50 % total cancer 60 non-cancer emission-weighted toxicity estimated for primary HAPs from anthropogenic biomass burning sources US, coverage higher (> 80 %) when formaldehyde acrolein are considered. In addition, new mechanism were added based importance their aerosol, or burden reactive carbon (ROC): sesquiterpenes, furans, propylene glycol, alkane-like low- intermediate-volatility compounds (9 species), oxygenated (16 aromatic hydrocarbons (2 slowly reacting carbon. Intermediate- lower-volatility increase ROC by 40 compared current operational mechanisms. Autoxidation, reaction particularly effective producing SOA, was C10 larger alkanes, hydrocarbons, monoterpene including second-generation aldehydes. Integrating radical SOA put additional constraints both enabled implementation previously unconsidered pathways phenolic furanone compounds, predicted account ∼ 30 hydrocarbon under typical conditions. found span atmospherically relevant range number, number oxygens per carbon, oxidation state slight high bias hydrogens total, 11 emitted implemented precursors CMAQv5.3.3 representations, resulting bottom-up prediction is required accurate source attribution design control strategies. available CMAQv5.4.

Language: Английский

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Measurement of the Intramolecular Hydrogen-Shift Rate Coefficient for the CH₃SCH₂OO Radical between 314 and 433 K

The Journal of Physical Chemistry A, Journal Year: 2023, Volume and Issue: 127(10), P. 2336 - 2350

Published: March 2, 2023

The intramolecular hydrogen-shift rate coefficient of the CH3SCH2O2 (methylthiomethylperoxy, MSP) radical, a product formed in oxidation dimethyl sulfide (DMS), was measured using pulsed laser photolysis flow tube reactor coupled to high-resolution time-of-flight chemical ionization mass spectrometer that formation DMS degradation end HOOCH2SCHO (hydroperoxymethyl thioformate). Measurements performed over temperature range 314–433 K yielded k1(T) = (2.39 ± 0.7) × 109 exp(−(7278 99)/T) s–1 Arrhenius expression and value extrapolated 298 0.06 s–1. potential energy surface have also been theoretically investigated density functional theory at M06-2X/aug-cc-pVTZ level combined with approximate CCSD(T)/CBS energies yielding k1(273–433 K) 2.4 1011 exp(−8782/T) k1(298 0.037 fair agreement experimental results. Present results are compared previously reported values k1(293–298 K).

Language: Английский

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