Radicals from the Gas-Phase Pyrolysis of Hydroquinone: 2. Identification of Alkyl Peroxy Radicals

2008 ◽  
Vol 22 (6) ◽  
pp. 3810-3813 ◽  
Author(s):  
Lavrent Khachatryan ◽  
Julien Adounkpe ◽  
Barry Dellinger
Keyword(s):  
Gas Phase ◽  
Peroxy Radicals ◽  
Alkyl Peroxy Radicals

scholarly journals α-pinene photooxidation under controlled chemical conditions – Part 1: Gas-phase composition in low- and high-NO<sub>x</sub> environments

2012 ◽  
Vol 12 (14) ◽  
pp. 6489-6504 ◽  
Author(s):  
N. C. Eddingsaas ◽  
C. L. Loza ◽  
L. D. Yee ◽  
J. H. Seinfeld ◽  
P. O. Wennberg
Keyword(s):  
Gas Phase ◽  
Carboxylic Acids ◽  
First Generation ◽  
Peroxy Radical ◽  
Organic Aerosol ◽  
Oxidation Products ◽  
Peroxy Radicals ◽  
Alkoxy Radical ◽  
Alkyl Peroxy Radicals ◽  
Chemical Conditions

Abstract. The OH oxidation of α-pinene under both low- and high-NOx environments was studied in the Caltech atmospheric chambers. Ozone was kept low to ensure OH was the oxidant. The initial α-pinene concentration was 20–50 ppb to ensure that the dominant peroxy radical pathway under low-NOx conditions is reaction with HO2, produced from reaction of OH with H2O2, and under high-NOx conditions, reactions with NO. Here we present the gas-phase results observed. Under low-NOx conditions the main first generation oxidation products are a number of α-pinene hydroxy hydroperoxides and pinonaldehyde, accounting for over 40% of the yield. In all, 65–75% of the carbon can be accounted for in the gas phase; this excludes first-generation products that enter the particle phase. We suggest that pinonaldehyde forms from RO2 + HO2 through an alkoxy radical channel that regenerates OH, a mechanism typically associated with acyl peroxy radicals, not alkyl peroxy radicals. The OH oxidation and photolysis of α-pinene hydroxy hydroperoxides leads to further production of pinonaldehyde, resulting in total pinonaldehyde yield from low-NOx OH oxidation of ~33%. The low-NOx OH oxidation of pinonaldehyde produces a number of carboxylic acids and peroxyacids known to be important secondary organic aerosol components. Under high-NOx conditions, pinonaldehyde was also found to be the major first-generation OH oxidation product. The high-NOx OH oxidation of pinonaldehyde did not produce carboxylic acids and peroxyacids. A number of organonitrates and peroxyacyl nitrates are observed and identified from α-pinene and pinonaldehyde.

scholarly journals α-pinene photooxidation under controlled chemical conditions – Part 1: Gas-phase composition in low- and high-NO<sub>x</sub> environments

2012 ◽  
Vol 12 (3) ◽  
pp. 6447-6483 ◽  
Author(s):  
N. C. Eddingsaas ◽  
C. L. Loza ◽  
L. D. Yee ◽  
J. H. Seinfeld ◽  
P. O. Wennberg
Keyword(s):  
Gas Phase ◽  
Carboxylic Acids ◽  
First Generation ◽  
Peroxy Radical ◽  
Organic Aerosol ◽  
Oxidation Products ◽  
Peroxy Radicals ◽  
Alkoxy Radical ◽  
Alkyl Peroxy Radicals ◽  
Chemical Conditions

Abstract. The OH oxidation of α-pinene under both low- and high-NOx environments was studied in the Caltech atmospheric chambers. Ozone was kept low to ensure OH was the oxidant. The initial α-pinene concentration was 20–50 ppb to ensure that the dominant peroxy radical pathway under low-NOx conditions is reaction with HO2 and under high-NOx conditions, reactions with NO. Here we present the gas-phase results observed. Under low-NOx conditions the main first generation oxidation products are α-pinene hydroxy hydroperoxide and pinonaldehyde, accounting for over 40% of the yield. In all, 65–75% of the carbon can be accounted for in the gas phase; this excludes first-generation products that enter the particle phase. We suggest that pinonaldehyde forms from RO2 + HO2 through an alkoxy radical channel that regenerates OH, a mechanism typically associated with acyl peroxy radicals, not alkyl peroxy radicals. The OH oxidation and photolysis of α-pinene hydroxy hydroperoxides leads to further production of pinonaldehyde, resulting in total pinonaldehyde yield from low-NOx OH oxidation of ~33%. The low-NOx OH oxidation of pinonaldehyde produces a number of carboxylic acids and peroxyacids known to be important secondary organic aerosol components. Under high-NOx conditions, pinonaldehyde was also found to be the major first-generation OH oxidation product. The high-NOx OH oxidation of pinonaldehyde did not produce carboxylic acids and peroxyacids. A number of organonitrates and peroxyacyl nitrates are observed and identified from α-pinene and pinonaldehyde.

Calculated Hydrogen Shift Rate Constants in Substituted Alkyl Peroxy Radicals

2018 ◽  
Vol 122 (43) ◽  
pp. 8665-8673 ◽  
Author(s):  
Rasmus V. Otkjær ◽  
Helene H. Jakobsen ◽  
Camilla Mia Tram ◽  
Henrik G. Kjaergaard
Keyword(s):  
Rate Constants ◽  
Peroxy Radicals ◽  
Hydrogen Shift ◽  
Alkyl Peroxy Radicals

scholarly journals Radicals in the marine boundary layer during NEAQS 2004: a model study of day-time and night-time sources and sinks

2009 ◽  
Vol 9 (9) ◽  
pp. 3075-3093 ◽  
Author(s):  
R. Sommariva ◽  
H. D. Osthoff ◽  
S. S. Brown ◽  
T. S. Bates ◽  
T. Baynard ◽  
...  
Keyword(s):  
Boundary Layer ◽  
New England ◽  
Gas Phase ◽  
Marine Boundary Layer ◽  
Peroxy Radical ◽  
Chemical Mechanism ◽  
Physical Parameters ◽  
Peroxy Radicals ◽  
Night Time ◽  
Aerosol Composition

Abstract. This paper describes a modelling study of several HOx and NOx species (OH, HO2, organic peroxy radicals, NO3 and N2O5) in the marine boundary layer. A model based upon the Master Chemical Mechanism (MCM) was constrained to observations of chemical and physical parameters made onboard the NOAA ship R/V Brown as part of the New England Air Quality Study (NEAQS) in the summer of 2004. The model was used to calculate [OH] and to determine the composition of the peroxy radical pool. Modelled [NO3] and [N2O5] were compared to in-situ measurements by Cavity Ring-Down Spectroscopy. The comparison showed that the model generally overestimated the measurements by 30–50%, on average. The model results were analyzed with respect to several chemical and physical parameters, including uptake of NO3 and N2O5 on fog droplets and on aerosol, dry deposition of NO3 and N2O5, gas-phase hydrolysis of N2O5 and reactions of NO3 with NMHCs and peroxy radicals. The results suggest that fog, when present, is an important sink for N2O5 via rapid heterogeneous uptake. The comparison between the model and the measurements were consistent with values of the heterogeneous uptake coefficient of N2O5 (γN2O5)>1×10−2, independent of aerosol composition in this marine environment. The analysis of the different loss processes of the nitrate radical showed the important role of the organic peroxy radicals, which accounted for a significant fraction (median: 15%) of NO3 gas-phase removal, particularly in the presence of high concentrations of dimethyl sulphide (DMS).

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 Peroxy Radical Chemistry and the Volatility Basis Set

2019 ◽  
Author(s):  
Meredith Schervish ◽  
Neil M. Donahue
Keyword(s):  
Temperature Dependence ◽  
Gas Phase ◽  
Organic Molecules ◽  
Peroxy Radical ◽  
Organic Aerosol ◽  
Basis Set ◽  
Strong Temperature Dependence ◽  
Peroxy Radicals ◽  
Cross Reactions ◽  
Oxidation Of Organics

Abstract. Gas-phase auto-oxidation of organics can generate highly-oxygenated organic molecules (HOMs) and thus increase secondary organic aerosol production and enable new-particle formation. Here we present a new implementation of the Volatility Basis Set (VBS) that explicitly resolves peroxy radicals (RO2) formed via auto-oxidation. The model includes a strong temperature dependence for auto oxidation as well as explicit termination of RO2, including reactions with NO, HO2, and other RO2. The RO2 cross reactions can produce dimers (ROOR). We explore the temperature and NOx dependence of this chemistry, showing that temperature strongly influences the intrinsic volatility distribution and that NO can suppress auto-oxidation under conditions typically found in the atmosphere.

Modeling the Organic Nitrate Yields in the Reaction of Alkyl Peroxy Radicals with Nitric Oxide. 2. Reaction Simulations

2003 ◽  
Vol 107 (38) ◽  
pp. 7434-7444 ◽  
Author(s):  
John R. Barker ◽  
Lawrence L. Lohr ◽  
Robert M. Shroll ◽  
Susan Reading
Keyword(s):  
Nitric Oxide ◽  
Organic Nitrate ◽  
Peroxy Radicals ◽  
Alkyl Peroxy Radicals

Quantitative product study of russell termination reactions of peroxy radicals in the gas phase

1981 ◽  
Vol 18 (1) ◽  
pp. 843-844 ◽  
Author(s):  
D.J. Bogan ◽  
J.J. Havel ◽  
R.A. Coveleskie ◽  
F. Celii ◽  
B.J. Stammerjohn ◽  
...  
Keyword(s):  
Gas Phase ◽  
Peroxy Radicals ◽  
Product Study
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