Kinetics and Products of the Reaction of the First-Generation Isoprene Hydroxy Hydroperoxide (ISOPOOH) with OH

Clair, Jason M. St.; Rivera-Rios, Jean C.; Crounse, J. D.; Knap, Hasse C.; Bates, Kelvin H.; Teng, Alexander P.; Jørgensen, Solvejg; Kjaergaard, Henrik G.; Keutsch, Frank N.; Wennberg, P. O.

doi:10.1021/acs.jpca.5b06532

Cited by 128 publications

(207 citation statements)

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“…The fractional yield of ISOPOOH in the reaction of ISOPOO with HO 2 is represented by the term Y ISOPOOH,HO 2 , which has an estimated value of 0.90 (35). By comparison, ISOPOOH is believed to be produced neither from the reactions of ISOPOO with NO and RO 2 nor by isomerization.…”

Section: Modelingmentioning

confidence: 99%

“…The fractions of the NO, HO 2 , RO 2 , and isomerization pathways sum to unity. These fractions were obtained for NO concentrations ranging from background to polluted conditions using a box model based on the Master Chemical Mechanism (version 3.3.1) and supplemented by recent experimental results (9,11,35). For straightforwardness, the OH concentration was held constant, although, in reality, it increased under polluted conditions (Fig.…”

Section: Modelingmentioning

confidence: 99%

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Isoprene photochemistry over the Amazon rainforest

Liu

Brito

Dorris

et al. 2016

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

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Isoprene photooxidation is a major driver of atmospheric chemistry over forested regions. Isoprene reacts with hydroxyl radicals (OH) and molecular oxygen to produce isoprene peroxy radicals (ISOPOO). These radicals can react with hydroperoxyl radicals (HO 2 ) to dominantly produce hydroxyhydroperoxides (ISOPOOH). They can also react with nitric oxide (NO) to largely produce methyl vinyl ketone (MVK) and methacrolein (MACR). Unimolecular isomerization and bimolecular reactions with organic peroxy radicals are also possible. There is uncertainty about the relative importance of each of these pathways in the atmosphere and possible changes because of anthropogenic pollution. Herein, measurements of ISOPOOH and MVK + MACR concentrations are reported over the central region of the Amazon basin during the wet season. The research site, downwind of an urban region, intercepted both background and polluted air masses during the GoAmazon2014/5 Experiment. Under background conditions, the confidence interval for the ratio of the ISOPOOH concentration to that of MVK + MACR spanned 0.4-0.6. This result implies a ratio of the reaction rate of ISOPOO with HO 2 to that with NO of approximately unity. A value of unity is significantly smaller than simulated at present by global chemical transport models for this important, nominally low-NO, forested region of Earth. Under polluted conditions, when the concentrations of reactive nitrogen compounds were high (>1 ppb), ISOPOOH concentrations dropped below the instrumental detection limit (<60 ppt). This abrupt shift in isoprene photooxidation, sparked by human activities, speaks to ongoing and possible future changes in the photochemistry active over the Amazon rainforest.isoprene photochemistry | Amazon | organic hydroperoxides

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Section: Modelingmentioning

confidence: 99%

Section: Modelingmentioning

confidence: 99%

Isoprene photochemistry over the Amazon rainforest

Liu

Brito

Dorris

et al. 2016

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

Self Cite

103

165

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“…So, for measured OH to be greater than modeled OH, there must be unknown OH sources, which could be either primary sources, such as photolysis of an unknown chemical species, or secondary sources, such as recycling of HO x to OH within the BVOC oxidation mechanisms. These discrepancies and the speculation about OH recycling have led to increased interest in the detailed chemical oxidation mechanisms for these BVOCs, particularly isoprene (Paulot et al 2009;Peeters et al 2009;Peeters and Müller 2010;Crounse et al 2011Crounse et al , 2012Crounse et al , 2013Praske et al 2015;St. Clair et al 2015).…”

Section: Introductionmentioning

confidence: 99%

Testing Atmospheric Oxidation in an Alabama Forest

Feiner

Brune

Miller

et al. 2016

Journal of the Atmospheric Sciences

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The chemical species emitted by forests create complex atmospheric oxidation chemistry and influence global atmospheric oxidation capacity and climate. The Southern Oxidant and Aerosol Study (SOAS) provided an opportunity to test the oxidation chemistry in a forest where isoprene is the dominant biogenic volatile organic compound. Hydroxyl (OH) and hydroperoxyl (HO 2 ) radicals were two of the hundreds of atmospheric chemical species measured, as was OH reactivity (the inverse of the OH lifetime). OH was measured by laser-induced fluorescence (LIF) and by taking the difference in signals without and with an OH scavenger that was added just outside the instrument's pinhole inlet. To test whether the chemistry at SOAS can be simulated by current model mechanisms, OH and HO 2 were evaluated with a box model using two chemical mechanisms: Master Chemical Mechanism, version 3.2 (MCMv3.2), augmented with explicit isoprene chemistry and MCMv3.3.1. Measured and modeled OH peak at about 10 6 cm 23 and agree well within combined uncertainties. Measured and modeled HO 2 peak at about 27 pptv and also agree well within combined uncertainties. Median OH reactivity cycled between about 11 s 21 at dawn and about 26 s 21 during midafternoon. A good test of the oxidation chemistry is the balance between OH production and loss rates using measurements; this balance was observed to within uncertainties. These SOAS results provide strong evidence that the current isoprene mechanisms are consistent with measured OH and HO 2 and, thus, capture significant aspects of the atmospheric oxidation chemistry in this isoprene-rich forest.

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“…Karl et al, 2006). The latter ones are formed without the involvement of nitric oxide (NO) so that ISOPOOH becomes increasingly important with decreasing concentrations of nitrogen oxides (St. Clair et al, 2015) which are mainly released by anthropogenic activities. The formation of MVK and MACR is accompanied by the production of HO 2 , which can further recycle OH, whereas ISOPOOH formation is a radical termination reaction.…”

Section: Introductionmentioning

confidence: 99%

Investigation of the oxidation of methyl vinyl ketone (MVK) by OH radicals in the atmospheric simulation chamber SAPHIR

Fuchs¹,

Albrecht²,

Acir

et al. 2018

Atmos. Chem. Phys.

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Abstract. The photooxidation of methyl vinyl ketone (MVK) was investigated in the atmospheric simulation chamber SAPHIR for conditions at which organic peroxy radicals (RO 2 ) mainly reacted with NO ("high NO" case) and for conditions at which other reaction channels could compete ("low NO" case). Measurements of trace gas concentrations were compared to calculated concentration time series applying the Master Chemical Mechanism (MCM version 3.3.1). Product yields of methylglyoxal and glycolaldehyde were determined from measurements. For the high NO case, the methylglyoxal yield was (19 ± 3) % and the glycolaldehyde yield was (65 ± 14) %, consistent with recent literature studies. For the low NO case, the methylglyoxal yield reduced to (5 ± 2) % because other RO 2 reaction channels that do not form methylglyoxal became important. Consistent with literature data, the glycolaldehyde yield of (37 ± 9) % determined in the experiment was not reduced as much as implemented in the MCM, suggesting additional reaction channels producing glycolaldehyde. At the same time, direct quantification of OH radicals in the experiments shows the need for an enhanced OH radical production at low NO conditions similar to previous studies investigating the oxidation of the parent VOC isoprene and methacrolein, the second major oxidation product of isoprene. For MVK the model-measurement discrepancy was up to a factor of 2. Product yields and OH observations were consistent with assumptions of additional RO 2 plus HO 2 reaction channels as proposed in literature for the major RO 2 species formed from the reaction of MVK with OH. However, this study shows that also HO 2 radical concentrations are underestimated by the model, suggesting that additional OH is not directly produced from RO 2 radical reactions, but indirectly via increased HO 2 . Quantum chemical calculations show that HO 2 could be produced from a fast 1,4-H shift of the second most important MVK derived RO 2 species (reaction rate constant 0.003 s −1 ). However, additional HO 2 from this reaction was not sufficiently large to bring modelled HO 2 radical concentrations into agreement with measurements due to the small yield of this RO 2 species. An additional reaction channel of the major RO 2 species with a reaction rate constant of (0.006 ± 0.004) s −1 would be required that produces concurrently HO 2 radicals and glycolaldehyde to achieve modelmeasurement agreement. A unimolecular reaction similar to the 1,5-H shift reaction that was proposed in literature for RO 2 radicals from MVK would not explain product yields for conditions of experiments in this study. A set of H-migration reactions for the main RO 2 radicals were investigated by quantum chemical and theoretical kinetic methodologies, but did not reveal a contributing route to HO 2 radicals or glycolaldehyde.

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Kinetics and Products of the Reaction of the First-Generation Isoprene Hydroxy Hydroperoxide (ISOPOOH) with OH

Cited by 128 publications

References 57 publications

Isoprene photochemistry over the Amazon rainforest

Isoprene photochemistry over the Amazon rainforest

Testing Atmospheric Oxidation in an Alabama Forest

Investigation of the oxidation of methyl vinyl ketone (MVK) by OH radicals in the atmospheric simulation chamber SAPHIR

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