Kinetics and mechanisms of the gas-phase reactions of ozone with organic compounds under atmospheric conditions

1984 ◽  
Vol 84 (5) ◽  
pp. 437-470 ◽  
Author(s):  
Roger Atkinson ◽  
William P. L. Carter
Keyword(s):  
Gas Phase ◽  
Organic Compounds ◽  
Atmospheric Conditions ◽  
Gas Phase Reactions

scholarly journals Different pathways of the formation of highly oxidized multifunctional organic compounds (HOMs) from the gas-phase ozonolysis of <i>β</i>-caryophyllene

2016 ◽  
Vol 16 (15) ◽  
pp. 9831-9845 ◽  
Author(s):  
Stefanie Richters ◽  
Hartmut Herrmann ◽  
Torsten Berndt
Keyword(s):  
Double Bond ◽  
Gas Phase ◽  
Organic Compounds ◽  
Atmospheric Pressure ◽  
Reaction System ◽  
Peroxy Radical ◽  
Closed Shell ◽  
Atmospheric Conditions ◽  
Reaction Products ◽  
Product Analysis

Abstract. The gas-phase mechanism of the formation of highly oxidized multifunctional organic compounds (HOMs) from the ozonolysis of β-caryophyllene was investigated in a free-jet flow system at atmospheric pressure and a temperature of 295 ± 2 K. Reaction products, mainly highly oxidized RO2 radicals containing up to 14 oxygen atoms, were detected using chemical ionization – atmospheric pressure interface – time-of-flight mass spectrometry with nitrate and acetate ionization. These highly oxidized RO2 radicals react with NO, NO2, HO2 and other RO2 radicals under atmospheric conditions forming the first-generation HOM closed-shell products. Mechanistic information on the formation of the highly oxidized RO2 radicals is based on results obtained with isotopically labelled ozone (18O3) in the ozonolysis reaction and from hydrogen/deuterium (H/D) exchange experiments of acidic H atoms in the products. The experimental findings indicate that HOM formation in this reaction system is considerably influenced by the presence of a double bond in the RO2 radicals primarily formed from the β-caryophyllene ozonolysis. Three different reaction types for HOM formation can be proposed, allowing for an explanation of the detected main products: (i) the simple autoxidation, corresponding to the repetitive reaction sequence of intramolecular H-abstraction of a RO2 radical, RO2  →  QOOH, and subsequent O2 addition, next forming a peroxy radical, QOOH + O2  →  R′O2; (ii) an extended autoxidation mechanism additionally involving the internal reaction of a RO2 radical with a double bond forming most likely an endoperoxide and (iii) an extended autoxidation mechanism including CO2 elimination. The individual reaction steps of the reaction types (ii) and (iii) are uncertain at the moment. From the product analysis it can be followed that the simple autoxidation mechanism accounts only for about one-third of the formed HOMs. Time-dependent measurements showed that the HOM formation proceeds at a timescale of 3 s or less under the concentration regime applied here. The new reaction pathways represent an extension of the mechanistic understanding of HOM formation via autoxidation in the atmosphere, as recently discovered from laboratory investigations on monoterpene ozonolysis.

scholarly journals Database for the kinetics of the gas-phase atmospheric reactions of organic compounds

2020 ◽  
Vol 12 (2) ◽  
pp. 1203-1216 ◽  
Author(s):  
Max R. McGillen ◽  
William P. L. Carter ◽  
Abdelwahid Mellouki ◽  
John J. Orlando ◽  
Bénédicte Picquet-Varrault ◽  
...  
Keyword(s):  
Gas Phase ◽  
Organic Compounds ◽  
Degradation Products ◽  
Rate Coefficients ◽  
Training Dataset ◽  
Gas Phase Reactions ◽  
Atmospheric Reactions ◽  
Temperature Dependences ◽  
Potential Applications ◽  
Kinetics Of

Abstract. We present a digital, freely available, searchable, and evaluated compilation of rate coefficients for the gas-phase reactions of organic compounds with OH, Cl, and NO3 radicals and with O3. Although other compilations of many of these data exist, many are out of date, most have limited scope, and all are difficult to search and to load completely into a digitized form. This compilation uses results of previous reviews, though many recommendations are updated to incorporate new or omitted data or address errors, and includes recommendations on many reactions that have not been reviewed previously. The database, which incorporates over 50 years of measurements, consists of a total of 2765 recommended bimolecular rate coefficients for the reactions of 1357 organic substances with OH, 709 with Cl, 310 with O3, and 389 with NO3, and is much larger than previous compilations. Many compound types are present in this database, including naturally occurring chemicals formed in or emitted to the atmosphere and anthropogenic compounds such as halocarbons and their degradation products. Recommendations are made for rate coefficients at 298 K and, where possible, the temperature dependences over the entire range of the available data. The primary motivation behind this project has been to provide a large and thoroughly evaluated training dataset for the development of structure–activity relationships (SARs), whose reliability depends fundamentally upon the availability of high-quality experimental data. However, there are other potential applications of this work, such as research related to atmospheric lifetimes and fates of organic compounds, or modelling gas-phase reactions of organics in various environments. This database is freely accessible at https://doi.org/10.25326/36 (McGillen et al., 2019).

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