scholarly journals Aqueous SOA formation from the photo-oxidation of vanillin: Direct photosensitized reactions and nitrate-mediated reactions

2021 ◽  
Author(s):  
Beatrix Rosette Go Mabato ◽  
Yan Lyu ◽  
Yan Ji ◽  
Dan Dan Huang ◽  
Xue Li ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Inorganic Anions ◽  
Decay Kinetics ◽  
Reaction Conditions ◽  
Photosensitized Oxidation ◽  
Photo Oxidation ◽  
Molar Ratios ◽  
Absorbance Changes ◽  
Triplet Excited States ◽  
Light Absorbance

Abstract. Vanillin (VL), a phenolic aromatic carbonyl abundant in biomass burning emissions, forms triplet excited states (3VL*) under simulated sunlight leading to aqueous secondary organic aerosol (aqSOA) formation. This direct photosensitized oxidation of VL was compared with nitrate-mediated VL photo-oxidation under atmospherically relevant cloud and fog conditions, through examining the VL decay kinetics, product compositions, and light absorbance changes. The majority of the most abundant products from both VL photo-oxidation pathways were potential Brown carbon (BrC) chromophores. In addition, both pathways generated oligomers, functionalized monomers, and oxygenated ring-opening products, but nitrate promoted functionalization and nitration, which can be ascribed to its photolysis products (•OH, •NO2, and N(III), NO2- or HONO). Moreover, a potential imidazole derivative observed from nitrate-mediated VL photo-oxidation suggested that ammonium may be involved in the reactions. The effects of secondary oxidants from 3VL*, pH, the presence of volatile organic compounds (VOCs) and inorganic anions, and reactants concentration and molar ratios on VL photo-oxidation were also explored. Our findings show that the secondary oxidants (1O2, O2•-/•HO2, •OH) from the reactions of 3VL* and O2 play an essential role in VL photo-oxidation. Enhanced oligomer formation was noted at pH < 4 and in the presence of VOCs and inorganic anions, probably due to additional generation of radicals (•HO2 and CO3•-). Also, functionalization was dominant at low VL concentration, whereas oligomerization was favored at high VL concentration. Furthermore, guaiacol oxidation by photosensitized reactions of VL was observed to be more efficient relative to nitrate-mediated photo-oxidation. Lastly, potential VL photo-oxidation pathways under different reaction conditions were proposed. This study indicates that the direct photosensitized oxidation of VL, which nitrate photolysis products can further enhance, may be an important aqSOA source in areas influenced by biomass burning emissions.

scholarly journals Aqueous secondary organic aerosol formation from the direct photosensitized oxidation of vanillin in the absence and presence of ammonium nitrate

2022 ◽  
Vol 22 (1) ◽  
pp. 273-293
Author(s):  
Beatrix Rosette Go Mabato ◽  
Yan Lyu ◽  
Yan Ji ◽  
Yong Jie Li ◽  
Dan Dan Huang ◽  
...  
Keyword(s):  
Ammonium Nitrate ◽  
Biomass Burning ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Simulated Sunlight ◽  
Aerosol Formation ◽  
Decay Kinetics ◽  
Photosensitized Oxidation ◽  
Fog Water ◽  
Molar Ratios

Abstract. Vanillin (VL), a phenolic aromatic carbonyl abundant in biomass burning emissions, forms triplet excited states (3VL∗) under simulated sunlight leading to aqueous secondary organic aerosol (aqSOA) formation. Nitrate and ammonium are among the main components of biomass burning aerosols and cloud or fog water. Under atmospherically relevant cloud and fog conditions, solutions composed of either VL only or VL with ammonium nitrate were subjected to simulated sunlight irradiation to compare aqSOA formation via the direct photosensitized oxidation of VL in the absence and presence of ammonium nitrate. The reactions were characterized by examining the VL decay kinetics, product compositions, and light absorbance changes. Both conditions generated oligomers, functionalized monomers, and oxygenated ring-opening products, and ammonium nitrate promoted functionalization and nitration, likely due to its photolysis products (⚫OH, ⚫NO2, and NO2- or HONO). Moreover, a potential imidazole derivative observed in the presence of ammonium nitrate suggested that ammonium participated in the reactions. The majority of the most abundant products from both conditions were potential brown carbon (BrC) chromophores. The effects of oxygen (O2), pH, and reactants concentration and molar ratios on the reactions were also explored. Our findings show that O2 plays an essential role in the reactions, and oligomer formation was enhanced at pH <4. Also, functionalization was dominant at low VL concentrations, whereas oligomerization was favored at high VL concentrations. Furthermore, oligomers and hydroxylated products were detected from the oxidation of guaiacol (a non-carbonyl phenol) via VL photosensitized reactions. Last, potential aqSOA formation pathways via the direct photosensitized oxidation of VL in the absence and presence of ammonium nitrate were proposed. This study indicates that the direct photosensitized oxidation of VL may be an important aqSOA source in areas influenced by biomass burning and underscores the importance of nitrate in the aqueous-phase processing of aromatic carbonyls.

Synthesis of a Ruthenium Complex Based on 2,6-Bis[1-(Pyridin-2-yl)-1H-Benzo[d]Imidazol-2-yl]Pyridine and Catalytic Oxidation of (1H-Benzo[d]-Imidazol-2-yl)Methanol to 1H-Benzo[d]Imidazole-2-Carbaldehyde with H2O2

2017 ◽  
Vol 41 (2) ◽  
pp. 88-92
Author(s):  
Shenggui Liu ◽  
Rongkai Pan ◽  
Wenyi Su ◽  
Guobi Li ◽  
Chunlin Ni
Keyword(s):  
Reaction Time ◽  
Catalytic Oxidation ◽  
Reaction Temperature ◽  
Ruthenium Complex ◽  
Reaction Conditions ◽  
Molar Ratios ◽  
Optimal Reaction

2,6-Bis[1-(pyridin-2-yl)-1H-benzo[d]-imidazol-2-yl]pyridine (bpbp), which has been synthesised by intramolecular thermocyclisation of N2,N6-bis[2-(pyridin-2-ylamino)phenyl]pyridine-2,6-dicarboxamide, reacts with sodium pyridine-2,6-dicarboxylate (pydic) and RuCl3 to give [Ru(bpbp)(pydic)] which can catalyse the oxidation of (1H-benzo[d]imidazol-2-yl)methanol to 1H-benzo[d]imidazole-2-carbaldehyde by H2O2. The optimal reaction conditions were: molar ratios of catalyst to substrate to H2O2 set at 1: 1000: 3000; reaction temperature 50 °C; reaction time 5 h. The yield of (1H-benzo[d]imidazol-2-yl) methanol was 70%.

Dodecanamide Concrete Foaming Agent: Preparation and Application

2011 ◽  
Vol 71-78 ◽  
pp. 799-802
Author(s):  
Cai Lin Liu ◽  
Yu Rong Zhang ◽  
Hai Jun Yang ◽  
Xian Yan Ren ◽  
Jun Xiao Yang
Keyword(s):  
Chloroacetic Acid ◽  
Foaming Properties ◽  
Dodecanoic Acid ◽  
Temperature Reaction ◽  
Synthetic Route ◽  
Foam Concrete ◽  
Reaction Conditions ◽  
Available N ◽  
Foaming Agent ◽  
Molar Ratios

A lauramide concrete foaming agent was prepared by a simple synthetic route using readily available N-(2-hydroxyethyl)ethylenediamine, dodecanoic acid, and chloroacetic acid. The reaction conditions were optimized by changing reaction temperature, reaction time, and/or molar ratios of reactants. Significantly, the concrete foaming agent has very low surface tension and good foaming properties, which could be directly used without purification and has widely applicable potentials in low-density foam concrete.

Joint impact of atmospheric SO2 and NH3 on the formation of nanoparticles from photo-oxidation of a typical biomass burning compound

2020 ◽  
Vol 7 (9) ◽  
pp. 2532-2545 ◽  
Author(s):  
Xiaotong Jiang ◽  
Chen Lv ◽  
Bo You ◽  
Zhiyi Liu ◽  
Xinfeng Wang ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Joint Effects ◽  
Photo Oxidation

The joint effects of SO2 and NH3 obviously promote the nanoparticles formation from the photooxidation of 3-methylfuran.

Preparation and Characterization of Ti-SBA-15 Mesoporous Materials with Varying Si/Ti Molar Ratios

2012 ◽  
Vol 482-484 ◽  
pp. 985-988
Author(s):  
Qiu Ying Huang ◽  
Wei Liu ◽  
Wen Hao Ye ◽  
Xiu Cheng Zheng
Keyword(s):  
Mesoporous Materials ◽  
Hydrothermal Process ◽  
Catalytic Efficiency ◽  
Mesoporous Structure ◽  
Catalytic Performance ◽  
Reaction Conditions ◽  
Molar Ratios ◽  
Good Catalytic Activity ◽  
Epoxidation Of Cyclohexene

Ti-SBA-15 mesoporous materials with different Si/Ti molar ratios were synthesized via a hydrothermal process and characterized by using various techniques. The effect of Si/Ti molar ratios in the gels on the structure and catalytic efficiency in epoxidation of cyclohexene was discussed in details. The results showed that all the Ti-SBA-15 materials retained SBA-15 mesoporous structure and exhibited good catalytic activity. Furthermore,the sample prepared with Si/Ti =50 exhibited the best catalytic performance under the reaction conditions.

Photosensitized oxidation of 9,10-dimethylanthracene with singlet oxygen by using a safranin O/silica composite under visible light

2015 ◽  
Vol 14 (3) ◽  
pp. 597-602 ◽  
Author(s):  
Elim Albiter ◽  
Salvador Alfaro ◽  
Miguel A. Valenzuela
Keyword(s):  
Visible Light ◽  
Singlet Oxygen ◽  
Second Step ◽  
Homogeneous Reaction ◽  
Photosensitized Oxidation ◽  
Photo Oxidation ◽  
The Third ◽  
Silica Composite ◽  
Safranin O

The photo-oxidation of DMA could be carried out in 3 steps: the first step is the photosensitized production of 1O2 near the surface of the composite; the second step is the diffusion of 1O2 from the surroundings of the surface to the solvent and the third step is the homogeneous reaction between 1O2 and DMA.

scholarly journals Antimalarial 9-Anilinoacridine Compounds Directed at Hematin

2003 ◽  
Vol 47 (12) ◽  
pp. 3708-3712 ◽  
Author(s):  
Saranya Auparakkitanon ◽  
Wilai Noonpakdee ◽  
Raymond K. Ralph ◽  
William A. Denny ◽  
Prapon Wilairat
Keyword(s):  
Topoisomerase Ii ◽  
Rapid Onset ◽  
Stoichiometric Ratio ◽  
The Novel ◽  
Dna Topoisomerase Ii ◽  
Dna Topoisomerase ◽  
Molar Ratios ◽  
Low Concentrations ◽  
Absorbance Changes

ABSTRACT Antimalarial 9-anilinoacridines are potent inhibitors of parasite DNA topoisomerase II both in vitro and in situ. 3,6-Diamino substitution on the acridine ring greatly improves parasiticidal activity against Plasmodium falciparum by targeting DNA topoisomerase II. A series of 9-anilinoacridines were investigated for their abilities to inhibitβ -hematin formation, to form drug-hematin complexes, and to enhance hematin-induced lysis of red blood cells. Inhibition ofβ -hematin formation was minimal with 3,6-diamino analogs of 9-anilinoacridine and greatest with analogs with a 3,6-diCl substitution together with an electron-donating group in the 1′-anilino position. On the other hand, the presence of a 1′-N(CH3)2 group in the anilino ring produced compounds that strongly inhibited β-hematin formation but which did not appear to be sensitive to the nature of the substitutions in the acridine nucleus. The derivatives bound hematin, and Job's plots of UV-visible absorbance changes in drug-hematin complexes at various molar ratios indicated a stoichiometric ratio of 1:2. The drugs enhanced hematin-induced red blood cell lysis at low concentrations (<4 μM). These studies open up the novel possibility of development of 9-anilinoacridine antimalarials that target not only DNA topoisomerase II but alsoβ -hematin formation, which should help delay the rapid onset of resistance to drugs acting at only a single site.

scholarly journals Optimization of the Lipase Catalyzed Production of Structured Acylglycerols With Polyunsaturated Fatty Acids Isolated From Sardine Oil

2013 ◽  
Vol 2 (6) ◽  
pp. 97 ◽  
Author(s):  
Juan Antonio Noriega-Rodriguez ◽  
Esther Carrillo-Perez ◽  
Nohemi Gamez-Meza ◽  
Luis A. Medina-Juarez ◽  
Ramiro Baeza-Jimenez ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Polyunsaturated Fatty Acids ◽  
Immobilized Lipase ◽  
Reaction Times ◽  
Molar Ratio ◽  
Reaction Conditions ◽  
Molar Ratios ◽  
Sardine Oil ◽  
Different Temperatures ◽  
Urea Crystallization

<p>In the present work, direct enzyme-catalyzed esterification of n-3 polyunsaturated fatty acids (n-3 PUFA) isolated from sardine oil was optimized to obtain structured acyglycerols. A n-3 PUFA concentrate was prepared by urea crystallization of refined sardine oil and esterification was carried out mixing free fatty acids and glycerol at different molar ratios (<em>M</em> = 0.48, 1.5, 3.0, 4.5 and 5.52 mol/mol), using an immobilized lipase preparation from <em>Candida antarctica</em> (NV-435) at different temperatures (<em>T</em> = 38, 45, 55, 65 and 72 °C) and reaction times (<em>t</em> = 0.7, 2.75, 5.75, 8.75 and 10.8 h) in a rotatable central composition design. The degree of esterification was determined by analysis of the acylglycerides produced, using liquid chromatography (HPLC-ELSD). Optimization by response surface methodology (RSM) showed that in order to obtain higher esterification levels of n-3 PUFA to glycerol (99.5%), a molar ratio of 1.3 mol n-3 PUFA/mol glycerol, time 8.3 h and temperature 38 °C, are required. However, results of this work show that it is possible to drive the reaction to any determined product (MAG, DAG or TAG) by modifying the reaction conditions.</p>

scholarly journals Chemical and physical transformations of organic aerosol from the photo-oxidation of open biomass burning emissions in an environmental chamber

2011 ◽  
Vol 11 (4) ◽  
pp. 11995-12037 ◽  
Author(s):  
C. J. Hennigan ◽  
M. A. Miracolo ◽  
G. J. Engelhart ◽  
A. A. May ◽  
A. A. Presto ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Organic Aerosol ◽  
Heterogeneous Reactions ◽  
Chemical Processing ◽  
Science Laboratory ◽  
Enhancement Ratio ◽  
Smog Chamber ◽  
Photo Oxidation ◽  
The Us ◽  
Mass Enhancement

Abstract. Smog chamber experiments were conducted to investigate chemical and physical transformations of organic aerosol (OA) during photo-oxidation of open biomass burning emissions. The experiments were carried out at the US Forest Service's Fire Science Laboratory as part of the third Fire Lab at Missoula Experiment (FLAME III). We investigated 12 different fuels commonly burned in North American wildfires. The experiments feature atmospheric and plume aerosol and oxidant concentrations; aging times ranged from 3–4.5 h. OA production, expressed as a mass enhancement ratio (ratio of OA to primary OA (POA) mass), was highly variable. OA mass enhancement ratios ranged from 2.9 in experiments where secondary OA (SOA) production nearly tripled the POA concentration, to 0.7 in experiments where photo-oxidation resulted in a 30% loss of the OA mass. The campaign-average OA mass enhancement ratio was 1.7 ± 0.7 (mean ± 1 σ); therefore, on average, there was substantial SOA production. In every experiment, the OA was chemically transformed. Even in experiments with net loss of OA mass, the OA became increasingly oxygenated and less volatile with aging, indicating that photo-oxidation transformed the POA emissions. Levoglucosan concentrations were also substantially reduced with photo-oxidation. The transformations of POA were extensive; using levoglucosan as a tracer for POA, unreacted POA only contributed 17% of the campaign-average OA mass after 3.5 h of exposure to typical atmospheric hydroxyl radical (OH) levels. Heterogeneous reactions with OH could account for less than half of this transformation, implying that the coupled gas-particle partitioning and reaction of semi-volatile vapors is an important and potentially dominant mechanism for POA processing. Overall, the results illustrate that biomass burning emissions are subject to extensive chemical processing in the atmosphere, and the timescale for these transformations is rapid.

scholarly journals Spectrophotometric determination of ascorbic acid by horseradish peroxidase

2020 ◽  
Vol 10 (2) ◽  
pp. 17-22
Author(s):  
Vladan Đurić ◽  
Nebojša Deletić
Keyword(s):  
Hydrogen Peroxide ◽  
Ascorbic Acid ◽  
Pharmaceutical Products ◽  
Reaction Conditions ◽  
Hydrogen Peroxide Decomposition ◽  
Peroxide Decomposition ◽  
Daily Dose ◽  
Ascorbate Concentration ◽  
Absorbance Changes

L-ascorbic acid is one of the essential nutrients and most common food supplements, fortificants, and preservatives. It is commercially available as solutions, drops, tablets, capsules, crystal powder, beverage mixtures, multivitamin formulations, and multi antioxidant formulations. The usual daily dose is from 25 mg to 1.5 g. Ascorbic acid is a distinctly reducing agent with low redox potential (0.18 and 0.08 V at pH 4.5 and 6.4, respectively). Based on ascorbate property, numerous methods for its quantitative determination are developed, from titrimetric, electrochemical, and chromatographic methods, to fluorometric and kinetic ones. Enzyme peroxidase is interfered with by ascorbic acid, which decreases the oxidation speed of its co-substrates during hydrogen peroxide decomposition by peroxidase. Absorbance changes at the wavelength of corresponding reagents are in correlation with ascorbate concentration. During this study, benzidine and o-tolidine have been used as chromogenic reagents. Reaction conditions were optimized for various buffer systems, calibration curves were constructed, and limits of detection (0.04 mmol/L) and quantification (0.12 mmol/L) were calculated. Using calibration charts, it was possible to detect ascorbic acid within limits from 0.4 to 10 mmol/L. The optimized method was applied for the determination of ascorbic acid in pharmaceutical products. The method was characterized by exceptional sensitivity and accuracy, but only for preparations not containing substances that affect enzyme peroxidase.

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