Atmospheric chemistry of oxazole: the mechanism and kinetic studies on oxidation reaction initiated by OH radicals

2021 ◽  
Author(s):  
Abolfazl Shiroudi ◽  
Mohamad Abdel-Rahman ◽  
Ahmed El-Nahas ◽  
Mohammednoor Altarawneh
Keyword(s):  
Reaction Kinetics ◽  
Atmospheric Chemistry ◽  
Oxidation Reaction ◽  
Kinetic Studies ◽  
Oh Radicals ◽  
Atmospheric Conditions

The oxidation reaction of oxazole initiated by OH radicals is studied via OH-addition and H-abstraction reactions using DFT (M06-2X and ωB97XD methods) under atmospheric conditions which coupled with reaction kinetics...

scholarly journals Comment on “Atmospheric chemistry of oxazole: the mechanism and kinetic studies on oxidation reaction initiated by OH radicals” by A. Shiroudi, M. A. Abdel-Rahman, A. M. El-Nahas and M. Altarawneh, New J. Chem., 2021, 45, 2237

2021 ◽  
Author(s):  
Tam V.-T. Mai ◽  
Lam K. Huynh
Keyword(s):  
Master Equation ◽  
Atmospheric Chemistry ◽  
Oxidation Reaction ◽  
Experimental Studies ◽  
Kinetic Studies ◽  
Oh Radicals ◽  
Rate Model

The large kinetic discrepancy between computational and experimental studies is resolved using the rigorous stochastic RRKM-based master-equation rate model. Detailed mechanistic insights are also revealed to advance its related applications.

Atmospheric chemistry of E-CF3CH CHCF3: Reaction kinetics of OH radicals and products of OH-initiated oxidation

2018 ◽  
Vol 706 ◽  
pp. 93-98 ◽  
Author(s):  
Feiyao Qing ◽  
Qin Guo ◽  
Liang Chen ◽  
Hengdao Quan ◽  
Junji Mizukado
Keyword(s):  
Reaction Kinetics ◽  
Atmospheric Chemistry ◽  
Oh Radicals ◽  
Kinetics Of

scholarly journals Characterization of a chemical modulation reactor (CMR) for the measurement of atmospheric concentrations of hydroxyl radicals with a laser-induced fluorescence instrument

2020 ◽  
Author(s):  
Changmin Cho ◽  
Andreas Hofzumahaus ◽  
Hendrik Fuchs ◽  
Hans-Peter Dorn ◽  
Marvin Glowania ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Trace Gases ◽  
Ambient Air ◽  
Laser Induced Fluorescence ◽  
Optical Absorption Spectroscopy ◽  
Oh Radicals ◽  
Atmospheric Conditions ◽  
Atmospheric Measurements ◽  
Chemical Modulation ◽  
Scavenging Efficiency

Abstract. Precise and accurate hydroxyl radical (OH) measurements are essential to investigate how trace gases are oxidized and transformed in the troposphere and how secondary pollutants like ozone (O3) are formed. Laser induced fluorescence (LIF) is a widely used technique for the measurement of ambient OH radicals and was used for the majority of field campaigns and chamber experiments. Recently, most LIF instruments in use for atmospheric measurements of OH radicals introduced chemical modulation to separate the ambient OH radical concentration from possible interferences by chemically removing ambient OH radicals before they enter the detection cell. In this study, we describe the application, characterization, and validation of a chemical modulation reactor (CMR) applied to the Forschungszentrum Jülich LIF (FZJ-LIF) instrument in use at the atmospheric simulation chamber SAPHIR. Besides dedicated experiments in synthetic air, the new technique was extensively tested during the year-round Jülich Atmospheric Chemistry Project (JULIAC) campaign, in which ambient air was continuously flowed into the SAPHIR chamber. It allowed performing OH measurement comparisons with Differential Optical Absorption Spectroscopy (DOAS) and investigation of interferences in a large variety of chemical and meteorological conditions. A good agreement was obtained in the LIF DOAS intercomparison within instrumental accuracies (18 % for LIF, 6.5 % for DOAS) which confirms that the new chemical modulation system of the FZJ-LIF instrument is suitable for measurement of interference-free OH concentrations. Known interferences from O3 + H2O and the nitrate radical (NO3) were quantified with the CMR in synthetic air in the chamber and found to be 3.0 × 105 cm-3 and 0.6 × 105 cm-3, respectively, for typical ambient air condition (O3 = 50 ppbv, H2O = 1 %, NO3 = 10 pptv). The interferences measured in ambient air during the JULIAC campaign in summer season had the median diurnal variation of the interference with a maximum daytime value of 0.9 × 106 cm-3 and a minimum nighttime value of 0.4 × 106 cm-3. The highest interference of 2 × 106 cm-3 occurred in a heat wave from 22–29 August, when the air temperature and ozone increased to 40 °C and 100 ppbv, respectively. All observed interferences could be fully explained by the known O3 + H2O interference, which is routinely corrected in FZJ-LIF measurements when no chemical modulation is applied. No evidence for unexplained interference was found during the JULIAC campaign. A kinetic chemical model of the chemical modulation reactor was developed and applied to estimate the possible perturbation of the OH transmission and scavenging efficiency by reactive atmospheric trace gases. These can remove OH by gas phase reactions in the reactor, or produce OH by non-photolytical reactions, most importantly by the reaction of ambient HO2 with NO. The interfering processes become relevant at high atmospheric OH reactivities. For the conditions of the JULIAC campaign with OH reactivities below 20 s-1, the influence on the determination of ambient OH concentrations was small (on average: 2 %). However, in environments with high OH reactivities, such as in a rain forest or megacity, the expected perturbation in the currently used chemical modulation reactor could be large (more than a factor of 2) and would need careful analysis and correction. This implies that chemical modulation, which was developed to eliminate interferences in ambient OH measurements, itself can be subject to interferences that depend on ambient atmospheric conditions.

New pathways of the reaction of OH radicals with dimethyl sulfide based on CH3SCH2O2 isomerization

2020 ◽  
Author(s):  
Torsten Berndt ◽  
Wiebke Scholz ◽  
Bernhard Mentler ◽  
Lukas Fischer ◽  
Erik Hans Hoffmann ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Dimethyl Sulfide ◽  
Peroxy Radical ◽  
Product Formation ◽  
Experimental Investigations ◽  
Oh Radicals ◽  
Atmospheric Conditions ◽  
Free Jet ◽  
Isomerization Process ◽  
Efficient Detection

<p>Dimethyl sulfide (DMS), produced by marine organisms, represents the most abundant, biogenic sulfur emission into the Earth´s atmosphere. The gas-phase degradation of DMS is mainly initiated by the reaction with the OH radical forming first CH<sub>3</sub>SCH<sub>2</sub>O<sub>2</sub> radicals from the dominant H-abstraction channel. A fast CH<sub>3</sub>SCH<sub>2</sub>O<sub>2</sub> isomerization process was proposed as a result of quantum chemical calculations. In the present study, experimental investigations on the product formation from OH + DMS have been conducted in a free-jet flow system at 295 ± 2 K and 1 bar air. Very efficient detection of CH<sub>3</sub>SCH<sub>2</sub>O<sub>2</sub> isomerization products has been achieved by iodide-CI-APi-TOF measurements allowing to run the reaction for close to atmospheric conditions. It is experimentally shown that the CH<sub>3</sub>SCH<sub>2</sub>O<sub>2</sub> radicals undergo a two-step isomerization process finally forming a product consistent with the formula HOOCH<sub>2</sub>SCHO. The isomerization process is accompanied by OH recycling. The rate-limiting first isomerization step, CH<sub>3</sub>SCH<sub>2</sub>O<sub>2</sub> → CH<sub>2</sub>SCH<sub>2</sub>OOH proceeds with k = (0.23 ± 0.12) s<sup>-1</sup> at 295 ± 2 K. Competing bimolecular CH<sub>3</sub>SCH<sub>2</sub>O<sub>2</sub> reactions with NO, HO<sub>2</sub> or RO<sub>2</sub> radicals are less important for trace-gas conditions over the oceans.  Results of atmospheric chemistry simulations demonstrate the predominance (≥95%) of CH<sub>3</sub>SCH<sub>2</sub>O<sub>2</sub> isomerization. The rapid peroxy radical isomerization, not yet considered in models, substantially changes the understanding of DMS´s degradation processes in the atmosphere.</p>

Impact Of Synthesis Route on the Water Oxidation Kinetics of Hematite Photoanodes

2020 ◽  
Author(s):  
Camilo A. Mesa ◽  
Ludmilla Steier ◽  
Benjamin Moss ◽  
Laia Francàs ◽  
James E. Thorne ◽  
...  
Keyword(s):  
Oxygen Vacancy ◽  
Reaction Kinetics ◽  
Water Oxidation ◽  
Oxidation Kinetics ◽  
Oxidation Reaction ◽  
Charge Accumulation ◽  
Optical Signals ◽  
Current Voltage ◽  
Voltage Performance ◽  
Kinetics Of

<p><i>Operando</i> spectroelectrochemical analysis is used to determine the water oxidation reaction kinetics for hematite photoanodes prepared using four different synthetic procedures. Whilst these photoanodes exhibit very different current / voltage performance, their underlying water oxidation kinetics are found to be almost invariant. Lower photoanode performance was found to correlate with the observation of optical signals indicative of charge accumulation in mid-gap oxygen vacancy states, indicating these states do not contribute directly to water oxidation.</p>

Atmospheric Chemistry of CH3CH2OCH3: Kinetics and Mechanism of Reactions with Cl Atoms and OH Radicals

2016 ◽  
Vol 49 (1) ◽  
pp. 10-20 ◽  
Author(s):  
Mads P. Sulbaek Andersen ◽  
Sissel Bjørn Svendsen ◽  
Freja From Østerstrøm ◽  
Ole John Nielsen
Keyword(s):  
Atmospheric Chemistry ◽  
Kinetics And Mechanism ◽  
Oh Radicals ◽  
Cl Atoms

Atmospheric chemistry of trans-CF3CHCHCl: Kinetics of the gas-phase reactions with Cl atoms, OH radicals, and O3

2008 ◽  
Vol 199 (1) ◽  
pp. 92-97 ◽  
Author(s):  
M.P. Sulbaek Andersen ◽  
E.J.K. Nilsson ◽  
O.J. Nielsen ◽  
M.S. Johnson ◽  
M.D. Hurley ◽  
...  
Keyword(s):  
Gas Phase ◽  
Atmospheric Chemistry ◽  
Oh Radicals ◽  
Gas Phase Reactions ◽  
Kinetics Of ◽  
Cl Atoms
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