scholarly journals Reactivity of a Carene-Derived Hydroxynitrate in Mixed Organic/Aqueous Matrices: Applying Synthetic Chemistry to Product Identification and Mechanistic Implications

Atmosphere ◽  
2021 ◽  
Vol 12 (12) ◽  
pp. 1617
Author(s):  
Addison B. McAlister ◽  
James I. Vesto ◽  
Aaron Huang ◽  
Kathryn A. Wright ◽  
Emily J. McLaughlin Sta. Maria ◽  
...  
Keyword(s):  
Water Concentration ◽  
Organic Aerosol ◽  
Organic Media ◽  
Product Yields ◽  
Major Class ◽  
Product Identification ◽  
Influence Of Water ◽  
Condensed Phase Reactions ◽  
Carbocation Rearrangement

β-hydroxynitrates (HN) are a major class of products formed during OH and NO3 initiated oxidation of terpenes. Their production contributes significantly to secondary organic aerosol (SOA) formation and NOx sequestration. However, studying the condensed phase reactions of this important class of molecules has been hindered by the lack of commercially available authentic standards. The goal of this work was to examine the influence of water concentration and solvent identity on product yields of a tertiary HN derived from 3-carene prepared in house. To assess the role of water on conversion chemistry, bulk-phase reactions were conducted in DMSO-d6, a non-nucleophilic solvent, with a gradient of water concentrations, and analyzed with 1H NMR. Product identifications were made by comparison with authentic standards prepared in house. Four major products were identified, including an unexpected diol produced from carbocation rearrangement, diol diastereomers, and trans-3-carene oxide, with varying yields as a function of water concentration. Product yields were also measured in two protic, nucleophilic solvents, MeOD-d4 and EtOD-d6. Finally, reactions with added chloride formed alkyl chloride products in yields approaching 30%. These results are among the first to highlight the complexities of nucleophilic reactions of hydroxynitrates in bulk, mixed aqueous/organic media and to identify new, unexpected products.

scholarly journals Aging of atmospheric aerosols and the role of iron in catalyzing brown carbon formation

2021 ◽  
Author(s):  
Hind A. A. Al-Abadleh
Keyword(s):  
Volatile Organic Compounds ◽  
Organic Compounds ◽  
Atmospheric Aerosols ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Atmospheric Oxidation ◽  
Carbon Formation ◽  
Brown Carbon ◽  
Volatile Organic

Extensive research has been done on the processes that lead to the formation of secondary organic aerosol (SOA) including atmospheric oxidation of volatile organic compounds (VOCs) from biogenic and anthropogenic...

scholarly journals Determining the Role of Acidity, Fate and Formation of IEPOX-Derived SOA in CMAQ

Atmosphere ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 707
Author(s):  
Petros Vasilakos ◽  
Yongtao Hu ◽  
Armistead Russell ◽  
Athanasios Nenes
Keyword(s):  
Significant Influence ◽  
Organic Aerosol ◽  
Liquid Water Content ◽  
Anthropogenic Emissions ◽  
So2 Emissions ◽  
Aerosol Acidity ◽  
A Value ◽  
Future Emission ◽  
The Impact

Formation of aerosol from biogenic hydrocarbons relies heavily on anthropogenic emissions since they control the availability of species such as sulfate and nitrate, and through them, aerosol acidity (pH). To elucidate the role that acidity and emissions play in regulating Secondary Organic Aerosol (SOA), we utilize the 2013 Southern Oxidant and Aerosol Study (SOAS) dataset to enhance the extensive mechanism of isoprene epoxydiol (IEPOX)-mediated SOA formation implemented in the Community Multiscale Air Quality (CMAQ) model (Pye et al., 2013), which was then used to investigate the impact of potential future emission controls on IEPOX OA. We found that the Henry’s law coefficient for IEPOX was the most impactful parameter that controls aqueous isoprene OA products, and a value of 1.9 × 107 M atm−1 provides the best agreement with measurements. Non-volatile cations (NVCs) were found in higher-than-expected quantities in CMAQ and exerted a significant influence on IEPOX OA by reducing its production by as much as 30% when present. Consistent with previous literature, a strong correlation of isoprene OA with sulfate, and little correlation with acidity or liquid water content, was found. Future reductions in SO2 emissions are found to not affect this correlation and generally act to increase the sensitivity of IEPOX OA to sulfate, even in extreme cases.

scholarly journals The Effect of Water Concentration in Ethyl Alcohol on the Environmentally Assisted Embrittlement of Austempered Ductile Irons

Metals ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 94
Author(s):  
Petar Janjatovic ◽  
Olivera Eric Cekic ◽  
Leposava Sidjanin ◽  
Sebastian Balos ◽  
Miroslav Dramicanin ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Cast Iron ◽  
Ultimate Tensile Strength ◽  
Ethyl Alcohol ◽  
Water Concentration ◽  
Different Types ◽  
Influence Of Water ◽  
Iron Material ◽  
Proof Strength

Austempered ductile iron (ADI) is an advanced cast iron material that has a broad field of application and, among others, it is used in contact and for conveyance of fluids. However, it is noticed that in contact with some fluids, especially water, ADI material becomes brittle. The most significant decrease is established for the elongation. However, the influence of water and the cause of this phenomenon is still not fully understood. For that reason, in this paper, the influence of different water concentrations in ethyl alcohol on the mechanical properties of ADI materials was studied. The test was performed on two different types of ADI materials in 0.2, 4, 10, and 100 vol.% water concentration environments, and in dry condition. It was found that even the smallest concentration of water (0.2 vol.%) causes formation of the embrittled zone at fracture surface. However, not all mechanical properties were affected equally and not all water concentrations have been critical. The highest deterioration was established in the elongation, followed by the ultimate tensile strength, while the proof strength was affected least.

scholarly journals Moisture Transport for Reaction Enhancement in Fabrics

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Phillip Gibson ◽  
Heidi Schreuder-Gibson ◽  
Pearl Yip ◽  
Brendan Denker ◽  
Hamid Benaddi ◽  
...  
Keyword(s):  
Bound Water ◽  
Nerve Agent ◽  
Vapor Transport ◽  
Reactive Polymers ◽  
Influence Of Water ◽  
Protective Polymer ◽  
Moisture Vapor ◽  
Protective Fabrics ◽  
Excessive Perspiration

The role of water in protective fabrics is critical to comfort and material performance. Excessive perspiration in clothing causes discomfort, and bound water can adversely affect the ability of carbon to adsorb chemicals. Yet the presence of water can also improve the moisture vapor transport of protective polymer films, and is essential for the hydrolytic destruction of nerve agents. Reported here are the findings of wicking and drying experiments conducted on various hydrophilic and hydrophobic cover fabrics that demonstrate the influence of wetting on permeation through fabrics. The influence of water content on reactive polymers capable of degrading nerve agent simulant is also discussed, and the importance of a novel “delivery system” for water to the reactive components through the use of a wicking fabric is introduced.

scholarly journals Radical mechanisms of methyl vinyl ketone oligomerization through aqueous phase OH-oxidation: on the paradoxical role of dissolved molecular oxygen

2013 ◽  
Vol 13 (1) ◽  
pp. 2913-2954 ◽  
Author(s):  
P. Renard ◽  
F. Siekmann ◽  
A. Gandolfo ◽  
J. Socorro ◽  
G. Salque ◽  
...  
Keyword(s):  
Aqueous Phase ◽  
High Resolution Mass Spectrometry ◽  
Organic Aerosol ◽  
Vinyl Ketone ◽  
Methyl Vinyl Ketone ◽  
Chemical Mechanism ◽  
Methyl Vinyl ◽  
Phase Chemistry ◽  
Dissolved O2

Abstract. It is now accepted that one of the important pathways of Secondary Organic Aerosol (SOA) formation occurs through aqueous phase chemistry in the atmosphere. However, the liquid phase chemical mechanisms leading to macromolecules are still not well understood. For α-dicarbonyl precursors, such as methylglyoxal and glyoxal, radical reactions through OH-oxidation produce oligomers, irreversibly and faster than accretion reactions. Methyl vinyl ketone (MVK) was chosen in the present study as it is an α, β-unsaturated carbonyl that can undergo such reaction pathways in the aqueous phase and forms even high molecular weight oligomers. We present here experiments on the aqueous phase OH-oxidation of MVK, performed under atmospheric relevant conditions. Using NMR and UV absorption spectroscopy, high and ultra-high resolution mass spectrometry, we show that the fast formation of oligomers up to 1800 Da is due to radical oligomerization of MVK, and 13 series of oligomers (out of a total of 26 series) are identified. The influence of atmospherically relevant parameters such as temperature, initial concentrations of MVK and dissolved oxygen are presented and discussed. In agreement with the experimental observations, we propose a chemical mechanism of OH-oxidation of MVK in the aqueous phase that proceeds via radical oligomerization of MVK on the olefin part of the molecule. This mechanism highlights the paradoxical role of dissolved O2: while it inhibits oligomerization reactions, it contributes to produce oligomerization initiator radicals, which rapidly consume O2, thus leading to the supremacy of oligomerization reactions after several minutes of reaction. These processes, together with the large ranges of initial concentrations investigated (60–656 μM of dissolved O2 and 0.2–20 mM of MVK) show the fundamental role that O2 likely plays in atmospheric organic aerosol.

scholarly journals Preformulation Studies on LACTUCA SATIVA as Nutraceuticals Granules

2013 ◽  
Vol 64 (2) ◽  
Author(s):  
Nagib Ali Elmarzugi ◽  
Eseldin Ibrahim Keleb ◽  
Aref Taleb Mohamed ◽  
Mohamed Salama ◽  
Mariani Abdul Hamid ◽  
...  
Keyword(s):  
Natural Products ◽  
Lactuca Sativa ◽  
Fine Powder ◽  
Water Concentration ◽  
Dosage Forms ◽  
Drying Methods ◽  
Solid Dosage Forms ◽  
Solid Dosage ◽  
Influence Of Water ◽  
Preformulation Studies

The utilization of natural products for their pharmaceutical and nutraceuticals purposes have high value in prevention and treatment of myriad illness. In pharmaceutical industry the formulation of natural products into an effective and stable dosage form necessitate evaluation of the processing techniques required and the properties of the product obtained. Therefore the objective of the present study was to prepare and evaluate lettuce leaves Lactuca sativa granules in a view to develop solid dosage forms. Lettuce leaves were washed with water, one batch was dried in open air and the other one in oven and grinded into fine powder. Dried powdered lettuce leaves were granulated without and with polyvinylpyrrolidone (PVP) at various water concentrations. The prepared granules were evaluated for its particle size distribution, bulk density, tapped density, hausners index, Carr’s index, friability, flowability and water absorption. The influence of water concentration, PVP addition and drying methods on the granule properties were also investigated. The results obtained showed that lettuce granules possess good flow properties and can be used as a candidate for the formulation of solid dosage forms particularly tablets.

scholarly journals Enhanced heterogenous hydration of SO 2 through immobilization of pyridinic-N on carbon materials

2020 ◽  
Vol 7 (8) ◽  
pp. 192248
Author(s):  
Longhua Zou ◽  
Ping Yan ◽  
Peng Lu ◽  
Dongyao Chen ◽  
Wei Chu ◽  
...  
Keyword(s):  
Gas Phase ◽  
Energy Barrier ◽  
Carbon Materials ◽  
Water Concentration ◽  
Flue Gases ◽  
Doped Graphene ◽  
Molecular Dynamics Results ◽  
Pyridinic N ◽  
Pyridinic Nitrogen

Carbon materials doped with nitrogen have long been used for SO 2 removal from flue gases for the benefits of the environment. The role of water is generally regarded as hydration of SO 3 which is formed through the oxidization of SO 2 . However, the hydration of SO 2 , especially on the surface of N-doped carbon materials, was almost ignored. In this study, the hydration of SO 2 was investigated in detail on the pyridinic nitrogen (PyN)-doped graphene (GP) surfaces. It is found that, compared with the homogeneous hydration of SO 2 assisted with NH 3 in gas phase, the heterogeneous hydration is much more thermodynamically and kinetically favourable. Specifically, when a single H 2 O molecule is involved, the energy barrier for SO 2 hydration is as low as 0.15 eV, with 0.59 eV released, indicating the hydration of SO 2 can occur at rather low water concentration and temperature. Thermodynamic integration molecular dynamics results show the feasibility of the hydrogenated substrate recovery and the immobilized N acting as a catalytic site for SO 2 hydration. Our findings show that the heterogeneous hydration of SO 2 should be universal and potentially uncover the puzzling reaction mechanism for SO 2 catalytic oxidation at low temperature by N-doped carbon materials.

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