The dependence of rate coefficients and product yields upon fluence, intensity, and time in unimolecular reactions induced by monochromatic infrared radiation

1980 ◽  
Vol 73 (1) ◽  
pp. 247-255 ◽  
Author(s):  
M. Quack ◽  
P. Humbert ◽  
H. van den Bergh
Keyword(s):  
Infrared Radiation ◽  
Rate Coefficients ◽  
Unimolecular Reactions ◽  
Product Yields

Reaction of OH with HO2NO2(Peroxynitric Acid):  Rate Coefficients between 218 and 335 K and Product Yields at 298 K

2004 ◽  
Vol 108 (7) ◽  
pp. 1139-1149 ◽  
Author(s):  
Elena Jiménez ◽  
Tomasz Gierczak ◽  
Harald Stark ◽  
James B. Burkholder ◽  
A. R. Ravishankara
Keyword(s):  
Rate Coefficients ◽  
Product Yields ◽  
Peroxynitric Acid

Double Bonds are Key to Fast Unimolecular Reactivity in First Generation Monoterpene Hydroxy Peroxy Radicals

2020 ◽  
Author(s):  
Jing Chen ◽  
Kristian H. Møller ◽  
Rasmus V. Otkjær ◽  
Henrik G. Kjaergaard
Keyword(s):  
Double Bond ◽  
Reaction Rate ◽  
First Generation ◽  
Rate Coefficients ◽  
Unimolecular Reaction ◽  
Peroxy Radicals ◽  
Double Bonds ◽  
Bimolecular Reactions ◽  
Unimolecular Reactions ◽  
Volatile Organic

<p>Monoterpenes are a group of volatile organic compounds that are emitted to the atmosphere in large amounts by natural sources. Some monoterpenes such as limonene and Δ<sup>3</sup>-carene are also widely used as additives in detergents and perfumes, and thus have a potential impact on indoor air quality and human health.</p><p>The volatile organic compounds like monoterpenes may undergo a series of autoxidation processes in the atmosphere to form highly oxygenated compounds, which have been linked to the formation of secondary organic aerosols. For this process to occur, the unimolecular reactions of the peroxy radicals formed during oxidation must have rate coefficients comparable to or greater than those of the competing bimolecular reactions with HO<sub>2</sub>, NO or other RO<sub>2</sub> radicals.</p><p>We studied the hydrogen shift (H-shift) and the cyclization reactions of all 45 hydroxy peroxy radicals formed by hydroxyl radical (OH) and O<sub>2</sub> addition to six monoterpenes (α-pinene, β-pinene, Δ<sup>3</sup>-carene, camphene, limonene and terpinolene). The reaction rate coefficients of the possible unimolecular reaction were initially studied at a lower level of theory. Those deemed likely to be atmospherically competitive were then calculated using the multi-conformer transition states theory approach developed by Møller et al. (J. Phys. Chem. A, 120, 51, 10072-10087, 2016). This approach has been shown to agree with the experimental values to within a factor of 4 for other systems.</p><p>It was found that double bonds are key to fast unimolecular reactions in the first-generation monoterpene hydroxy peroxy radicals. The H-shift reactions abstracting a hydrogen from a carbon adjacent to a double bond are found to typically be fast enough to compete with the bimolecular reactions, likely due to the resonance stability of the nascent allylic radical. The reactivity of the cyclization reaction between the carbon-carbon double bonds and the peroxy group, which forms an endoperoxide ring, is high as well. The H-shifts abstracting the hydrogen from the hydroxy group may be competitive in some cases but the reaction rate coefficients for these reactions are more uncertain. Generally, the cyclization reaction and the allylic H-shift reactions are the dominant reaction paths for the studied peroxyl radicals. Since the OH radical addition consumes one double bond, we suggest that the monoterpenes with more than one double bond in their structure are likely to have unimolecular reactions that can be important for the first-generation monoterpene peroxy radicals. On the other hand, the ones with only one double bond initially are not likely to have fast unimolecular reactions that can compete with the bimolecular reactions under the atmospheric condition, unless a double bond can be formed during their oxidation process as found for α-pinene and β-pinene. This result greatly limits the amount of potentially important unimolecular reaction paths in atmospheric monoterpene oxidation.</p>

scholarly journals Computed Rate Coefficients and Product Yields forc-C5H5+ CH3→ Products

2009 ◽  
Vol 113 (31) ◽  
pp. 8871-8882 ◽  
Author(s):  
Sandeep Sharma ◽  
William H. Green
Keyword(s):  
Rate Coefficients ◽  
Product Yields

Pressure dependence of the rate coefficients and product yields for the reaction of CH3CO radicals with O2

1997 ◽  
Vol 29 (9) ◽  
pp. 655-663 ◽  
Author(s):  
Geoffrey S. Tyndall ◽  
John J. Orlando ◽  
Timothy J. Wallington ◽  
Michael D. Hurley
Keyword(s):  
Pressure Dependence ◽  
Rate Coefficients ◽  
Product Yields

scholarly journals Atmospheric oxidation of α,β-unsaturated ketones: kinetics and mechanism of the OH radical reaction

2021 ◽  
Author(s):  
Niklas Illmann ◽  
Rodrigo Gastón Gibilisco ◽  
Iustinian Gabriel Bejan ◽  
Iulia Patroescu-Klotz ◽  
Peter Wiesen
Keyword(s):  
Radical Reaction ◽  
Rate Coefficients ◽  
Organic Nitrates ◽  
Oh Radicals ◽  
Oh Radical ◽  
Peroxyacetyl Nitrate ◽  
Unsaturated Ketones ◽  
Product Yields ◽  
Mechanistic Investigation ◽  
Cl Atoms

Abstract. The OH radical initiated oxidation of 3-methyl-3-penten-2-one and 4-methyl-3-penten-2-one was investigated in two atmospheric simulation chambers at 298 ± 3 K and 990 ± 15 mbar using long-path FTIR spectroscopy. The rate coefficients of the reactions of 3-methyl-3-penten-2-one and 4-methyl-3-penten-2-one with OH radicals were determined to be (6.5 ± 1.2) × 10−11 cm3 molecule−1 s−1 and (8.1 ± 1.3) × 10−11 cm3 molecule−1 s−1, respectively. To enlarge the kinetics data pool the rate coefficients of the target species with Cl atoms were determined to be (2.8 ± 0.4) × 10−10 cm3 molecule−1 s−1 and (3.1 ± 0.4) × 10−10 cm3 molecule−1 s−1, respectively. The mechanistic investigation of the OH initiated oxidation focuses on the RO2 + NO reaction. The quantified products were acetoin, acetaldehyde, biacetyl, CO2 and peroxyacetyl nitrate (PAN) for the reaction of 3-methyl-3-penten-2-one with OH radicals and acetone, methyl glyoxal, 2-hydroxy-2-methylpropanal, CO2 and peroxyacetyl nitrate (PAN) for the reaction of 4-methyl-3-penten-2-one with OH, respectively. Based on the calculated product yields an upper limit of 0.15 was determined for the overall organic nitrates (RONO2) yield derived from the OH reaction of 4-methyl-3-penten-2-one. By contrast, no RONO2 formation was observed for the OH reaction of 3-methyl-3-penten-2-one. Additionally, a simple model is presented to correct product yields for secondary processes.

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