Atmospheric Oxidation of Propanesulfinic Acid Initiated by OH Radicals: Reaction Mechanism, Energetics, Rate Coefficients, and Atmospheric Implications

2021 ◽  
Author(s):  
Parandaman Arathala ◽  
Rabi A. Musah
Keyword(s):  
Reaction Mechanism ◽  
Atmospheric Oxidation ◽  
Rate Coefficients ◽  
Oh Radicals

Rate Coefficients and Mechanisms of Atmospheric Oxidation of the Esters

2011 ◽  
Author(s):  
Jack Calvert ◽  
Abdelwahid Mellouki ◽  
John Orlando ◽  
Michael Pilling ◽  
Timothy Wallington
Keyword(s):  
Vegetable Oils ◽  
Methyl Esters ◽  
Ambient Air ◽  
Consumer Products ◽  
Anthropogenic Sources ◽  
Atmospheric Oxidation ◽  
Rate Coefficients ◽  
Oh Radicals ◽  
Loss Mechanism ◽  
Animal Fats

Esters are emitted directly into the atmosphere from both natural and anthropogenic sources and are produced during the atmospheric oxidation of ethers. Methyl acetate and ethyl acetate have found widespread use as solvents. Vegetable oils and animal fats are esters. Transesterification of vegetable oils and animal fats with methanol gives fatty acid methyl esters (FAMEs) which are used in biodiesel. Many esters have pleasant odors and are present in essential oils, fruits, and pheromones, and are often added to fragrances and consumer products to provide a pleasant odor. Table VII-A-1 provides a list of common esters and their odors. It is surprising to note that despite their ubiquitous nature, volatility, and fragrance, it is only very recently that quantitative measurements of esters in ambient air have been reported (Niedojadlo et al., 2007; Legreid et al., 2007). The atmospheric oxidation of saturated esters is largely initiated by OH radical attack. Reaction with O3 and NO3 radicals contributes to the atmospheric oxidation of unsaturated esters. As discussed in chapter IX, UV absorption by esters is only important for wavelengths below approximately 240 nm and, hence, photolysis is not a significant tropospheric loss mechanism. When compared to the ethers from which they can be derived, the esters are substantially less reactive towards OH radicals. The ester functionality —C(O)O— in R1C(O)OR2 deactivates the alkyl groups to which it is attached with the deactivation being most pronounced for the R1 group attached to the carbonyl group. The atmospheric oxidation mechanisms of the esters are reviewed in the present chapter. The reaction of OH with methyl formate has been studied by Wallington et al. (1988b) and Le Calvé et al. (1997a) over the temperature range 233–372 K. Data are summarized in table VII-B-1 and are plotted in figure VII-B-1. The room temperature determination of k(OH + CH3OCHO) by Wallington et al. is in agreement with that by Le Calvé et al. (1997) within the experimental uncertainties. Significant curvature is evident in the Arrhenius plot in figure VII-B-1.

scholarly journals Oxidation reaction mechanism and kinetics between OH radicals and alkyl-substituted aliphatic thiols: OH-addition pathways

2019 ◽  
Vol 44 (2) ◽  
pp. 157-174 ◽  
Author(s):  
Arezoo Tahan ◽  
Abolfazl Shiroudi
Keyword(s):  
Reaction Mechanism ◽  
Rate Constants ◽  
Effective Rate ◽  
Activation Energies ◽  
State Theory ◽  
Rate Coefficients ◽  
Oh Radicals ◽  
Oxidation Reactions ◽  
Kinetic Rate ◽  
Kinetic Rate Constants

Kinetic rate constants for the oxidation reactions of OH radicals with CH3SH (1), C2H5SH (2), n-C3H7SH (3) and iso-C3H7SH (4) under inert conditions (Ar) over the temperature range 252−430 K have been studied using the CBS-QB3 composite method. Kinetic rate constants under atmospheric pressure and in the fall-off regime have been estimated using transition state theory (TST) and statistical Rice–Ramsperger–Kassel–Marcus (RRKM) theory. Comparison with experiment confirms that in the OH-addition pathways 1−4 leading to the related products, the first bimolecular reaction step has effective negative activation energies around −2.61 to 3.70 kcal mol−1. Effective rate coefficients have been calculated according to a steady-state analysis of a two-step model reaction mechanism. As a result of the negative activation energies, pressures larger than 104 bar would be required to restore to some extent the validity of this approximation for all the channels. By comparison with experimental data, all our calculations for both the OH-addition and H-abstraction reaction pathways indicate that from a kinetic viewpoint and in line with the computed reaction energy barriers, the most favourable process is the OH-addition pathway to n-C3H7SH to yield the [ n-C3H7SH−OH]• species, whereas under thermodynamic control of the bimolecular reactions (R−SH+OH•), the most abundant product derived from the H-abstraction pathway will be the [ n-C3H7 S•+H2O] species.

Determination of Complex Reaction Mechanisms

2006 ◽  
Author(s):  
John Ross ◽  
Igor Schreiber ◽  
Marcel O. Vlad
Keyword(s):  
Reaction Mechanism ◽  
Reaction Mechanisms ◽  
Reaction Pathway ◽  
Chemical Species ◽  
Rate Coefficients ◽  
Chemical System ◽  
Evolutionary Development ◽  
Complex Reaction ◽  
Oscillatory Reactions

In a chemical system with many chemical species several questions can be asked: what species react with other species: in what temporal order: and with what results? These questions have been asked for over one hundred years about simple and complex chemical systems, and the answers constitute the macroscopic reaction mechanism. In Determination of Complex Reaction Mechanisms authors John Ross, Igor Schreiber, and Marcel Vlad present several systematic approaches for obtaining information on the causal connectivity of chemical species, on correlations of chemical species, on the reaction pathway, and on the reaction mechanism. Basic pulse theory is demonstrated and tested in an experiment on glycolysis. In a second approach, measurements on time series of concentrations are used to construct correlation functions and a theory is developed which shows that from these functions information may be inferred on the reaction pathway, the reaction mechanism, and the centers of control in that mechanism. A third approach is based on application of genetic algorithm methods to the study of the evolutionary development of a reaction mechanism, to the attainment given goals in a mechanism, and to the determination of a reaction mechanism and rate coefficients by comparison with experiment. Responses of non-linear systems to pulses or other perturbations are analyzed, and mechanisms of oscillatory reactions are presented in detail. The concluding chapters give an introduction to bioinformatics and statistical methods for determining reaction mechanisms.

Temperature dependent rate coefficients for the reaction of OH radicals with dimethylbenzoquinones

2015 ◽  
Vol 639 ◽  
pp. 145-150 ◽  
Author(s):  
Iustinian Bejan ◽  
Ian Barnes ◽  
Peter Wiesen ◽  
John C. Wenger
Keyword(s):  
Rate Coefficients ◽  
Oh Radicals ◽  
Temperature Dependent ◽  
Dependent Rate

scholarly journals Role of Criegee intermediates in the formation of sulfuric acid at a Mediterranean (Cape Corsica) site under influence of biogenic emissions

2021 ◽  
Vol 21 (17) ◽  
pp. 13333-13351
Author(s):  
Alexandre Kukui ◽  
Michel Chartier ◽  
Jinhe Wang ◽  
Hui Chen ◽  
Sébastien Dusanter ◽  
...  
Keyword(s):  
Steady State ◽  
Sulfuric Acid ◽  
Organic Compounds ◽  
Rate Coefficients ◽  
Oh Radicals ◽  
Additional Source ◽  
So2 Oxidation ◽  
Criegee Intermediates ◽  
Volatile Organic

Abstract. Reaction of stabilized Criegee intermediates (SCIs) with SO2 was proposed as an additional pathway of gaseous sulfuric acid (H2SO4) formation in the atmosphere, supplementary to the conventional mechanism of H2SO4 production by oxidation of SO2 in reaction with OH radicals. However, because of a large uncertainty in mechanism and rate coefficients for the atmospheric formation and loss reactions of different SCIs, the importance of this additional source is not well established. In this work, we present an estimation of the role of SCIs in H2SO4 formation at a western Mediterranean (Cape Corsica) remote site, where comprehensive field observations including gas-phase H2SO4, OH radicals, SO2, volatile organic compounds (VOCs) and aerosol size distribution measurements were performed in July–August 2013 as a part of the project ChArMEx (Chemistry-Aerosols Mediterranean Experiment). The measurement site was under strong influence of local emissions of biogenic volatile organic compounds, including monoterpenes and isoprene generating SCIs in reactions with ozone, and, hence, presenting an additional source of H2SO4 via SO2 oxidation by the SCIs. Assuming the validity of a steady state between H2SO4 production and its loss by condensation on existing aerosol particles with a unity accommodation coefficient, about 90 % of the H2SO4 formation during the day could be explained by the reaction of SO2 with OH. During the night the oxidation of SO2 by OH radicals was found to contribute only about 10 % to the H2SO4 formation. The accuracy of the derived values for the contribution of OH + SO2 reaction to the H2SO4 formation is limited mostly by a large, at present factor of 2, uncertainty in the OH + SO2 reaction rate coefficient. The contribution of the SO2 oxidation by SCIs to the H2SO4 formation was evaluated using available measurements of unsaturated VOCs and steady-state SCI concentrations estimated by adopting rate coefficients for SCI reactions based on structure–activity relationships (SARs). The estimated concentration of the sum of SCIs was in the range of (1–3) × 103 molec. cm−3. During the day the reaction of SCIs with SO2 was found to account for about 10 % and during the night for about 40 % of the H2SO4 production, closing the H2SO4 budget during the day but leaving unexplained about 50 % of the H2SO4 formation during the night. Despite large uncertainties in used kinetic parameters, these results indicate that the SO2 oxidation by SCIs may represent an important H2SO4 source in VOC-rich environments, especially during nighttime.

THE RADIOLYSIS OF ALKALINE AQUEOUS SOLUTIONS CONTAINING HYDROGEN AND OXYGEN

1966 ◽  
Vol 44 (6) ◽  
pp. 737-741 ◽  
Author(s):  
W. A. Armstrong
Keyword(s):  
Reaction Mechanism ◽  
Radical Reactions ◽  
Alkaline Solutions ◽  
Oh Radicals ◽  
Neutral Solution ◽  
A Value ◽  
Rate Of Reaction ◽  
Γ Rays ◽  
Ph Range ◽  
The Relationship

The initial yields of H2O2 in aerated water, [Formula: see text] and in water containing H2 and O2, [Formula: see text] have been measured for alkaline solutions irradiated with 60Co γ-rays. [Formula: see text] decreases with increasing pH from a value of 1.22 in neutral solution to 0.63 in solutions of pH 13.92 and the relationship[Formula: see text]is valid over the pH range 7 to 14.[Formula: see text] decreases from 3.30 in neutral solution to a minimum of 2.00 at pH 11.35 and then increases to 2.65 at pH 13.92. The equation[Formula: see text]which is applicable for neutral solutions, is not valid for basic solutions.A reaction mechanism in accordance with the observed results and the literature values of the rate constants of likely radical reactions has been developed. It is assumed that in the alkaline solutions investigated OH radicals react with OH− ions to form O− radicals which react preferentially with O2 to form O3− radicals which then react either with H2 or H2O2. The increase in [Formula: see text] at PH > 12 is attributed to a difference in the rate of reaction of O3− with H2O2 and HO2−, k(O3− + H2O2)/k(O3− + HO2−) = 2.45.

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