Investigation of organic nitrate product formation during hydroxyl radical initiated photo-oxidation of β-pinene

2011 ◽  
Vol 45 (1) ◽  
pp. 26-34 ◽  
Author(s):  
Janeen Auld ◽  
Donald R. Hastie
Keyword(s):  
Hydroxyl Radical ◽  
Product Formation ◽  
Organic Nitrate ◽  
Photo Oxidation

scholarly journals Impact of NO<sub>x</sub> on secondary organic aerosol (SOA) formation from <i>α</i>-pinene and <i>β</i>-pinene photo-oxidation: the role of highly oxygenated organic nitrates

2020 ◽  
Author(s):  
Iida Pullinen ◽  
Sebastian Schmitt ◽  
Sungah Kang ◽  
Mehrnaz Sarrafzadeh ◽  
Patrick Schlag ◽  
...  
Keyword(s):  
Gas Phase ◽  
Functional Groups ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Organic Nitrate ◽  
Organic Nitrates ◽  
Peroxy Radicals ◽  
Photo Oxidation ◽  
Mass Formation

Abstract. The formation of organic nitrates (ON) in the gas phase and their impact on mass formation of Secondary Organic Aerosol (SOA) was investigated in a laboratory study for α-pinene and β-pinene photo-oxidation. Focus was the elucidation of those mechanisms that cause the often observed suppression of SOA mass formation by NOx, and therein the role of highly oxygenated multifunctional molecules (HOM). We observed that with increasing NOx (a) the portion of HOM organic nitrates (HOM-ON) increased, (b) the fraction of accretion products (HOM-ACC) decreased and (c) HOM-ACC contained on average smaller carbon numbers. Specifically, we investigated HOM organic nitrates (HOM-ON), arising from the termination reactions of HOM peroxy radicals with NOx, and HOM permutation products (HOM-PP), such as ketones, alcohols or hydroperoxides, formed by other termination reactions. Effective uptake coefficients γeff of HOM on particles were determined. HOM with more than 6 O-atoms efficiently condensed on particles (γeff > 0.5 in average) and for HOM containing more than 8 O-atoms, every collision led to loss. There was no systematic difference in γeff for HOM-ON and HOM-PP arising from the same HOM peroxy radicals. This similarity is attributed to the multifunctional character of the HOM: as functional groups in HOM arising from the same precursor HOM peroxy radical are identical, vapor pressures should not strongly depend on the character the final termination group. As a consequence, the suppressing effect of NOx on SOA formation cannot be simply explained by replacement of terminal functional groups by organic nitrate groups. The fraction of organic bound nitrate (OrgNO3) stored in gas-phase HOM-ON appeared to be substantially higher than the fraction of particulate OrgNO3 observed by aerosol mass spectrometry. This result suggests losses of OrgNO3 for organic nitrates in particles, probably due to hydrolysis of OrgNO3 that releases HNO3 into the gas phase but leaves behind the organic rest in the particulate phase. However, the loss of HNO3 alone, could not explain the observed suppressing effect of NOx on particle mass formation from α-pinene and β-pinene. We therefore attributed most of the reduction in SOA mass yields with increasing NOx to the significant suppression of gas-phase HOM-ACC which have high molecular mass and are potentially important for SOA mass formation at low NOx conditions.

scholarly journals A product study of the isoprene+NO<sub>3</sub> reaction

2009 ◽  
Vol 9 (14) ◽  
pp. 4945-4956 ◽  
Author(s):  
A. E. Perring ◽  
A. Wisthaler ◽  
M. Graus ◽  
P. J. Wooldridge ◽  
A. L. Lockwood ◽  
...  
Keyword(s):  
Thermal Dissociation ◽  
Organic Aerosol ◽  
Proton Transfer Reaction ◽  
Product Formation ◽  
Oxidation Products ◽  
Organic Nitrate ◽  
Organic Nitrates ◽  
Isoprene Nitrates ◽  
Additional Constraints ◽  
Product Study

Abstract. Oxidation of isoprene through reaction with NO3 radicals is a significant sink for isoprene that persists after dark. The main products of the reaction are multifunctional nitrates. These nitrates constitute a significant NOx sink in the nocturnal boundary layer and they likely play an important role in formation of secondary organic aerosol. Products of the isoprene+NO3 reaction will, in many locations, be abundant enough to affect nighttime radical chemistry and to persist into daytime where they may represent a source of NOx. Product formation in the isoprene + NO3 reaction was studied in a smog chamber at Purdue University. Isoprene nitrates and other hydrocarbon products were observed using Proton Transfer Reaction-Mass Spectrometry (PTR-MS) and reactive nitrogen products were observed using Thermal Dissociation–Laser Induced Fluorescence (TD-LIF). The organic nitrate yield is found to be 65±12% of which the majority was nitrooxy carbonyls and the combined yield of methacrolein and methyl vinyl ketone (MACR+MVK) is found to be ∼10%. PTR-MS measurements of nitrooxy carbonyls and TD-LIF measurements of total organic nitrates agreed well. The PTR-MS also observed a series of minor oxidation products which were tentatively identified and their yields quantified These other oxidation products are used as additional constraints on the reaction mechanism.

scholarly journals Aqueous-Phase Production of Secondary Organic Aerosols from Oxidation of Dibenzothiophene (DBT)

Atmosphere ◽  
2020 ◽  
Vol 11 (2) ◽  
pp. 151 ◽  
Author(s):  
Yu Liu ◽  
Junchen Lu ◽  
Yanfang Chen ◽  
Yue Liu ◽  
Zhaolian Ye ◽  
...  
Keyword(s):  
Hydroxyl Radical ◽  
Aqueous Phase ◽  
Reaction Pathway ◽  
Photochemical Reactions ◽  
Oxidation Products ◽  
Gas Phase Reactions ◽  
Photo Oxidation ◽  
Oxygenated Compounds ◽  
Direct Light ◽  
Triplet Excited States

Intermediate-volatility organic compounds (IVOCs) have been recognized as an important contributor to the secondary organic aerosol (SOA) formation via gas-phase reactions. However, it is unclear whether or not IVOCs-SOA can be produced in the aqueous phase. This work investigated aqueous oxidation of one model compound of IVOCs, dibenzothiophene (DBT). Results show that DBT can be degraded by both hydroxyl radical and the triplet excited states of organic light chromophores (3C*). Aqueous dark oxidation of DBT was also possible. SOA yields of 32% and 15% were found for hydroxyl radical (OH)-mediated photo-oxidation and dark oxidation, respectively. A continuous and significant increase of oxidation degree of SOA was observed during OH photo-oxidation, but not during the dark oxidation. Factor analyses revealed that there was a persistent production of highly oxygenated compounds from the less oxygenated species. OH-initiated photochemical reactions can also produce species with a relatively large light-absorbing ability, while such photo-enhancement due to direct light irradiation and 3C*-initiated oxidation could occur, but is much less important. In the future, studies on the second-order rate constants, molecular characterization of the oxidation products from this and other IVOCs precursors are needed to better understand the role of this reaction pathway in SOA budget, air quality and climate change.

Redox reactions with ferrocene/ferricenium species of radicals derived by H atom abstraction from alcohols and diols

1991 ◽  
Vol 69 (3) ◽  
pp. 540-544 ◽  
Author(s):  
S. R. Logan
Keyword(s):  
Electron Transfer ◽  
Hydroxyl Radical ◽  
Key Words ◽  
Rate Constants ◽  
Redox Reactions ◽  
Radical Reactions ◽  
Dehydration Process ◽  
Photo Oxidation ◽  
Redox Behaviour ◽  
Vicinal Diols

The effect of various alcohols and diols in diminishing the extent of the photo-oxidation of 4-ferrocenylbutanoate ion in the presence of N2O has been investigated. Where the hydroxyl radical generated in the photo-initiated electron transfer reacts with an alcohol by H atom abstraction at the α-position, the resulting radical is capable of reducing the ferricenium zwitterion to the ferrocenyl anion. Abstraction at other positions produces radicals that are essentially inert in this system and rate constants are derived for the reaction of OH with some such compounds. Non-vicinal diols behave similarly to the corresponding alcohols. With vicinal diols, a dehydration process, which occurs the more slowly the more highly substituted the diol, converts the radical -CR(OH)Ċ(OH)- into -ĊRCO-, which is an oxidizing species. The behaviour of pinacol was found to be anomalous. Key words: radical reactions, redox behaviour, alcohols.

scholarly journals A product study of the isoprene+NO<sub>3</sub> reaction

2009 ◽  
Vol 9 (1) ◽  
pp. 5231-5261 ◽  
Author(s):  
A. E. Perring ◽  
A. Wisthaler ◽  
M. Graus ◽  
P. J. Wooldridge ◽  
A. L. Lockwood ◽  
...  
Keyword(s):  
Carbonyl Compounds ◽  
Thermal Dissociation ◽  
Organic Aerosol ◽  
Proton Transfer Reaction ◽  
Product Formation ◽  
Oxidation Products ◽  
Organic Nitrate ◽  
Isoprene Nitrates ◽  
Additional Constraints ◽  
Product Study

Abstract. Oxidation of isoprene through reaction with NO3 is a significant sink for isoprene that persists after dark. The products of the reaction are multifunctional nitrates. These nitrates constitute a significant NOx sink in the nocturnal boundary layer and they likely play an important role in formation of secondary organic aerosol. Products of the isoprene+NO3 reaction will, in many locations, be abundant enough to affect nighttime radical chemistry and to persist into daytime where they may represent a source of NOx. Product formation in the isoprene+NO3 reaction was studied in a smog chamber at Purdue University. Isoprene nitrates and other hydrocarbon products were observed using Proton Transfer Reaction-Mass Spectrometry (PTR-MS) and reactive nitrogen products were observed using Thermal Dissociation–Laser Induced Fluorescence (TD-LIF). The organic nitrate yield is found to be 62±6% and the combined yield of MACR+MVK is found to be ~10%. Additional hydrocarbon products, thought to be primarily C4 and C5 carbonyl compounds, were observed by the PTR-MS at various m/z ratios and their yields quantified. These other oxidation products are used as additional constraints on the reaction mechanism.

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