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1
Maleki, Behrooz. "An efficient synthesis of 2-arylbenzothiazoles using silica sulfuric acid, oxalic acid and aluminum chloride hydrate as heterogeneous and homogeneous catalyst systems". Collection of Czechoslovak Chemical Communications 76, n. 1 (6 dicembre 2010): 27–37. http://dx.doi.org/10.1135/cccc2010111.
Testo completoAbstract (sommario):
A convenient method for the synthesis of 2-arylbenzothiazoles from condensation of aromatic/heteroaromatic aldehydes with 2-aminothiophenol has been developed using inexpensive, green and reusable solid acids – silica sulfuric acid (SSA), oxalic acid or AlCl3·6H2O as efficient catalysts. The reactions occurred under mild conditions to afford the corresponding 2-arylbenzothiazoles in good to excellent yields.
2
Bensalah, Nasr, Mohamed F. Ahmadi e Abdelatif Gadri. "Electrochemical treatment of wastewaters containing 4-nitrocathecol using boron-doped diamond anodesA paper submitted to the Journal of Environmental Engineering and Science." Canadian Journal of Civil Engineering 36, n. 4 (aprile 2009): 683–89. http://dx.doi.org/10.1139/s08-054.
Testo completoAbstract (sommario):
The electrochemical oxidation of aqueous wastes polluted with 4-nitrocathecol has been studied on boron-doped diamond electrodes in an acidic medium. The voltammetric results showed that 4-nitrocathecol is oxidized in the potential region where the supporting electrolyte is stable. Galvanostatic electrolysis study showed that the oxidation of these wastes in a single-compartment electrochemical flow cell with boron-doped diamond anodes results in the complete mineralization of the organics. Cathecol, benzoquinone, 4-aminocathecol, maleic and oxalic acids have been detected as soluble organics, polymeric product as solid product at the cathode surface and NO3– as mineral product during the electrolysis of 4-nitrocathecol. The electrochemical oxidation of 4-nitrocathecol consists of a sequence of steps: release of NO2 and (or) hydroxylation of the aromatic ring; formation of quinonic compounds; oxidative opening of aromatic ring to form carboxylic acids; and oxidation of carboxylic acids to carbon dioxide. Both direct and mediated oxidation processes are involved in these stages.
3
Piccolo, A., G. Pietramellara e G. Celano. "Iron extractability from iron-humate complexes by a siderophore and a mixture of organic acids". Canadian Journal of Soil Science 73, n. 3 (1 agosto 1993): 293–98. http://dx.doi.org/10.4141/cjss93-031.
Testo completoAbstract (sommario):
Two well-characterized humic acids (HA), extracted from a volcanic soil and a leonhardite, were used to synthesize insoluble Fe complexes. The complexes were treated at different concentrations and contact times with a siderophore (deferoxamine mesylate) and a mixture of simple organic acids (citric, oxalic, tartaric, and ketoglutaric acids) naturally occurring in root exudates in order to evaluate the capacity of the extracting solutions to desorb Fe from the humic complexes. Results showed that iron can be extracted from the complexes according to the concentrations and pH of the extractants. The mixture of organic acids was generally a better extractant than the siderophore at the high concentration because of lower solution pH. Despite constant differences in solution pH, the extracting capacity of the two extractants was similar at lower concentrations. However, the extent of desorption varied with HA characteristics. Iron appeared to be more easily released from complexes with HA rich in aliphatic carbons than from those with HA rich in aromatic carbons. These findings were attributed to the stereochemical complexity of highly aromatic humic substances that prevents natural chelators to easily reach the Fe complexing sites. Key words: Humic substances, iron, siderophores, organic acids, plant chlorosis
4
Shanaida, Mariia, e Alina Holenko. "CHROMATOGRAPHIC ANALYSIS OF CARBOXYLIC ACIDS IN THE FLOWERING SHOOTS OF SOME Vitex L. SPECIES". Acta Medica Leopoliensia 28, n. 1-2 (30 giugno 2022): 99–103. http://dx.doi.org/10.25040/aml2022.1-2.099.
Testo completoAbstract (sommario):
Introduction. The genus Vitex L. counts more than 200 species of shrubs and trees common to subtropical areas of the Earth. Only fruits of Vitex agnus-castus L. are used in official medicine.
The aim of our study was to perform the chromatographic analysis of carboxylic acids in the flowering shoots of three Vitex representatives under their cultivation in Ukraine.
Materials and Methods. Gas chromatography with mass spectrometry (GC/MS) was applied for the analysis of composition and contents of carboxylic acids in the Vitex agnus-castus L., Vitex negundo L. and Vitex negundo var. cannabifolia (Siebold & Zucc.) Hand.-Mazz. flowering shoots.
Results and Discussion. The Vitex agnus-castus raw material contained the most significant amount of short-chained aliphatic acids (2454 mg/kg). Malonic, oxalic, citric, and malic acids noticeably prevailed in all the raw materials. The largest amount of aromatic acids was found in the Vitex negundo var. cannabifolia (3926 mg/kg) flowering shoots. p-Hydroxybenzoic acid dominated among the aromatic acids in the plant raw materials of all species. The most noticeable total content of unsaturated fatty acids was in the Vitex negundo var. cannabifolia (4793 mg/kg).
Conclusions. To summarize the contents of valuable carboxylic acids, the obtained results provide the evidence for the development and further pharmacological study of herbal preparations from the flowering shoots of three Vitex species.
5
Xie, Yuanyuan, e Suping Wang. "PhI(OAc)2-Mediated One-Pot Synthesis of Benzoxazinones from Anthranilic Acids and Aromatic Aldehydes". Journal of Chemical Research 36, n. 3 (marzo 2012): 123–26. http://dx.doi.org/10.3184/174751912x13285455672357.
Testo completoAbstract (sommario):
A novel way to synthesise 2-aryl-4H-benzo[d][1,3]oxazin-4-ones has been developed by the cyclisation of Schiff bases with (diacetoxyiodo)benzene. The salient features of this new protocol which starts from an anthranilic acid and an aromatic aldehyde, are short reaction time, mild reaction conditions and good yields.
6
Bi, Zhihao, Zhihao Li e Lifeng Yan. "Catalytic oxidation of lignin to dicarboxylic acid over the CuFeS2 nanoparticle catalyst". Green Processing and Synthesis 7, n. 4 (26 luglio 2018): 306–15. http://dx.doi.org/10.1515/gps-2017-0056.
Testo completoAbstract (sommario):
AbstractCuFeS2nanoparticles have been synthesized and used as catalyst for the degradation of lignin. Under mild condition of reaction at 60°C and 5 h in the presence of 2 ml hydrogen peroxide, lignin can be degraded completely and converted to dicarboxylic acids, such as oxalic acid (OA), fumaric acid, maleic acid, and succinic acid (SA), carbon oxides, and aromatic compounds. The major product is OA (up to 30% selectivity) and SA. On the basis of the chemicals detected, we proposed a logical mechanism similar to Fenton reaction. The results reveal that HO˙ and HOO−, formed from the cleavage of hydrogen peroxide over the catalyst, play an essential role in the oxidation of lignin to destroy its aromatic structure and generate carboxylic or DCA. This is a potential method to convert native lignin as a renewable feedstock to produce valuable chemicals.
7
Quesada, J., F. Teffo-Bertaud, J. P. Croué e M. Rubio. "Ozone Oxidation and Structural Features of an Almond Shell Lignin Remaining after Furfural Manufacture". Holzforschung 56, n. 1 (6 febbraio 2002): 32–38. http://dx.doi.org/10.1515/hf.2002.006.
Testo completoAbstract (sommario):
Summary Wastes from industrial processes which use lignocellulosic materials as raw material are an interesting source of chemicals since they can be transformed into products of high added value. In the process described here, ozone was used to produce oxyaromatics from a lignin-rich industrial waste resulting from the production of furfural from almond shells. Ozonation, thioacidolysis and mild alkaline hydrolysis were used to determine some structural features of the raw and acid-hydrolyzed almond shell lignins. During ozone treatment of the different lignin solutions the following compounds were identified: glycolic, oxalic, malonic, glyceric (trace), malic, p-hydroxybenzoic and vanillic acids, p-hydroxybenzaldehyde, vanillin, syringaldehyde and hydroquinone. The aromatic aldehydes passed through a production maximum during the first few minutes of the reaction, while glycolic and oxalic acid (the main aliphatic acids) yields increased throughout the treatment. Raw almond shell lignin had a typical hardwood composition [made up of guaiacyl (G) and syringyl (S) phenylpropane units] and few β-O-4 structures. Acid-hydrolyzed almond shell lignins had a more condensed structure than the above. The S/G ratio obtained by ozonation was slightly lower than that obtained by thioacidolysis, with the (S/G)Ozonation/(S/G)Thioacidolysis ratio ranging from 0.52 to 0.70. The almond shell lignin-polysaccharide complex did not contain any cell wall-esterified p-hydroxycinnamic acid (p-coumaric and ferulic acids).
8
Zhang, Qiang, Kai Mu, Bo Zhao e Linlin Yi. "The Role of the Mannich Reaction in Nitrogen Migration during the Co-Hydrothermal Carbonization of Bovine Serum Albumin and Lignin with Various Forms of Acid–Alcohol Assistance". Molecules 28, n. 11 (29 maggio 2023): 4408. http://dx.doi.org/10.3390/molecules28114408.
Testo completoAbstract (sommario):
Co-hydrothermal carbonization (co-HTC) of N-rich and lignocellulosic biomass is a potential way to produce hydrochar with high yield and quality, but the nitrogen will also enrich in a solid product. In this study, a novel co-HTC with acid–alcohol assistance is proposed, and the model compounds bovine serum albumin (BSA) and lignin were used to investigate the role of the acid–alcohol-enhanced Mannich reaction in nitrogen migration. The results showed that the acid–alcohol mixture could inhibit nitrogen enrichment in solids and the order of the denitrification rate was acetic acid > oxalic acid > citric acid. Acetic acid promoted solid-N hydrolysis to NH4+ while oxalic acid preferred to convert it to oil-N. More tertiary amines and phenols were generated with oxalic acid–ethanol addition and then formed quaternary-N and N-containing aromatic compounds through the Mannich reaction. In the citric acid–ethanol–water solution, NH4+ and amino acids were captured to form diazoxide derivatives in oil and pyrroles in solids through both nucleophilic substitution and the Mannich reaction. The results are able to guide biomass hydrochar production with the targeted regulation of nitrogen content and species.
9
Maduwanthi, S. D. T., e R. A. U. J. Marapana. "Comparative Study on Aroma Volatiles, Organic Acids, and Sugars of Ambul Banana (Musa acuminata, AAB) Treated with Induced Ripening Agents". Journal of Food Quality 2019 (10 ottobre 2019): 1–9. http://dx.doi.org/10.1155/2019/7653154.
Testo completoAbstract (sommario):
The present study was conducted to investigate effect of induced ripening agents on aroma profile, organic acids and sugars of Ambul banana (Musa acuminata, AAB). Mature green bananas that are in same maturity stage were subjected to 1000 ppm ethephon and 1000 ppm acetylene and kept at 20°C, 80–85% RH for ripening. Aroma profile was analyzed by SPME-GC-MS, while organic acids and sugars were tested by HPLC. Naturally ripened banana was found to be more aromatic than acetylene- and ethephon-treated banana having highest number of volatile compounds (27) and high level of esters (65%). Malic acid, citric acid, and oxalic acids were significantly low in treated bananas compared to naturally ripened bananas. Glucose and fructose, which are major types of sugars in ripe banana flesh, were significantly low in acetylene-treated banana, while sucrose was not detected in both ethephon- and acetylene-treated samples at fully yellow stage. Although ethephon and acetylene trigger the ripening process, they lead to poor aroma profile and lower levels of organic acids and sugars in flesh of banana.
10
Annor-Gyamfi, Joel K., e Richard A. Bunce. "4H-Benzo[d][1,3]oxazin-4-ones and Dihydro Analogs from Substituted Anthranilic Acids and Orthoesters". Molecules 24, n. 19 (1 ottobre 2019): 3555. http://dx.doi.org/10.3390/molecules24193555.
Testo completoAbstract (sommario):
A one-pot route to 2-alkyl and 2-aryl-4H-benzo[d][1,3]oxazin-4-ones (also known as 4H-3,1-benzoxazin-4-ones) has been developed and studied. The method involves the reaction of aryl-substituted anthranilic acids with orthoesters in ethanol catalyzed by acetic acid. Additionally, we have also investigated the reaction under microwave conditions. Not all of the substrates were successful in yielding the target heterocycles as some of the reactions failed to undergo the final elimination. This process led to the isolation of (±)-2-alkyl/aryl-2-ethoxy-1,2-dihydro-4H-benzo[d][1,3]oxazin-4-ones. The formation of the dihydro analogs correlated with the electron density on the aromatic ring: Electron-donating groups favored the 4H- benzo[d][1,3]oxazin-4-ones, while electron-withdrawing groups tended to favor the dihydro product. Substituting a pyridine ring for the benzene ring in the substrate acid suppressed the reaction.
11
Гордєй, К. Р., e Т. М. Гонтова. "Study on the composition of fatty and organic acids of the feverfew herb (Tanacetum Parthenium (L.) Schultz Bip.)". Farmatsevtychnyi zhurnal, n. 5 (1 ottobre 2020): 61–67. http://dx.doi.org/10.32352/0367-3057.5.20.07.
Testo completoAbstract (sommario):
In recent years, herbal medicines have become increasingly popular for the treatment of many diseases because they have a complex and multifactorial influence on the body. Fatty and organic acids are important groups of biologically active substances for the improvement of many pathological human’s conditions. Feverfew (Tanacetum parthenium (L.) Schultz Bip.) is a promising source of biologically active substances with many years of success in medicine and insufficiently studied chemical composition. The analysis of fatty and organic acids is one of the directions of our comprehensive study of the feverfew herb grown in Ukraine.
The aim of the work was to conduct a study of the qualitative composition and quantitative content of fatty and organic acids in the feverfew herb grown in Ukraine.
For the study, we used the feverfew herb, which was grown in the scientific fields of the Botanical Garden of the National University of Ukraine (2019). The studies were carried out by a gas chromatography-mass spectrometric method on an Agilent Technologies 6890N chromatograph with a 5973 mass spectrometric detector.
35 carboxylic acids were found and identified in the samples. Among them 21 acids are saturated, 5 are unsaturated and 9 are aromatic. The total content of carboxylic acids in feverfew herb was 26.54 mg/g. Among the identified fatty and organic acids in the feverfew herb the greatest amount of the following acids was observed: succinic (4.89 mg/g), levulinic (4.34 mg/g), citric (2.73 mg/g), palmitic (2.15 mg/g), linoleic (1.71 mg/g), oxalic (1.53 mg/g) and linolenic (1.07 mg/g) acids. Among the aromatic acids in the feverfew herb the dominant compounds were p-coumaric (2.4%), benzoic (1.89%) and ferulic (1.40%).
For the first time, a chromatography-mass spectrometric determination of the qualitative composition and quantitative content of organic and fatty acids in feverfew herb collected in Ukraine was carried out. The data obtained indicate a varied composition and rich content of acids in domestic raw materials and will be used to create medicines based on the feverfew herb.
12
Ribeiro, Rui S., Adrián M. T. Silva, Helder T. Gomes e Joaquim L. Faria. "High-performance liquid chromatography as a tool to evaluate the performance of the catalytic wet peroxide oxidation of 4-nitrophenol: pre-validation of analytical methods". U.Porto Journal of Engineering 1, n. 1 (6 settembre 2017): 50–66. http://dx.doi.org/10.24840/2183-6493_001.001_0006.
Testo completoAbstract (sommario):
A high-performance liquid chromatography (HPLC) method capable to detect 4-nitrophenol (4-NP) in aqueous solutions with concentration in the range 0.0495-118.8 mg L-1 was developed and validated under the typical criteria for in -house pre-validations. Accordingly, linearity was demonstrated through the Fisher’s exact probability test. Accuracy and precision were then assessed in three concentrationlevels over the linear range. The reproducibility of the catalytic wet peroxide oxidation (CWPO) of 4-NP was evaluated together with the analytical error of 4-NP determination in independent experiments. In this case, the sum of both contributions to error never reached 3%.Two multi-component HPLC methods were also developed for the determination of possible aromatic intermediates (hydroquinone, 1,4-benzoquinone, catechol, 4-nitrocatechol and phenol) and carboxylic acids (oxalic, formic, malic, malonic, acetic and maleic acids) resulting from the 4-NP degradation. The combination of these analytical methods already led to the proposal of an oxidation/mineralization mechanism for the CWPO of 4-NP.
13
Faly, Liudmyla, Viktor Brygadyrenko e Algimantas Paulauskas. "Repellent and Attractant Activities of Organic Compounds on Female and Male Philonthus decorus (Coleoptera, Staphylinidae)". Biology 13, n. 5 (25 aprile 2024): 294. http://dx.doi.org/10.3390/biology13050294.
Testo completoAbstract (sommario):
The use of organic compounds in different spheres of human activity is accompanied by their influx to and accumulation in the environment. The negative impact of those compounds can be one of the reasons for a decline in populations and biodiversity of aboveground invertebrates. Chemical compounds can potentially cause a variety of effects (attractant or repellent) on insects, including species of the Staphylinidae family. In a laboratory experiment, we identified repellent and attractant influence of 40 organic compounds and mixtures of compounds (acids, alcohols, ketones, phenols, aldehydes, aromatic carbohydrates solvents, and vehicle fuels) on Philonthus decorus Gravenhorst, 1802. The ambulatory responses of the males and females to the same chemical compounds most often varied. A strong repellent activity against both sexes of Ph. decorus was caused by oleic acid, while hexane repelled the males. Acetic acid, 1-butanol, and ammonia solution were found to be strongly repellent against females. A moderate (average) repellent activity towards male Ph. decorus was displayed by organic solvents and fuels, some alcohols (isopropanol, isoamyl alcohol, methanol, ethanol), acids (acetic, formic acid), aromatic carbohydrates (toluene, xylene), and formaldehyde. Female Ph. decorus in general were less sensitive to the odors. The list of repellents with moderate activity against the females was much shorter: solvent 646, white spirit, toluene, isopropanol, isoamyl alcohol, citric and oxalic acids, and glycerol. Moderate attractant activity for Ph. decorus was exhibited by some amino acids, alcohols, and fuel mixes: glycine and L-cysteine (for the males), and phenylalanine, methanol, and diesel fuel (for the females). The rest of the 40 chemical compounds we studied caused no ambulatory responses in Ph. decorus. The difficulties we encountered in the interpretation of the results suggest a need for further experimental studies that would expand the knowledge of the chemoecology of insects.
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Falkovich, A. H., E. R. Graber, G. Schkolnik, Y. Rudich, W. Maenhaut e P. Artaxo. "Low molecular weight organic acids in aerosol particles from Rondônia, Brazil, during the biomass-burning, transition and wet periods". Atmospheric Chemistry and Physics Discussions 4, n. 5 (28 ottobre 2004): 6867–907. http://dx.doi.org/10.5194/acpd-4-6867-2004.
Testo completoAbstract (sommario):
Abstract. Particles from biomass burning and regional haze were sampled in Rondônia, Brazil, during dry, transition and wet periods from September to November 2002, as part of the LBA-SMOCC (Large-Scale Biosphere-Atmosphere Experiment in Amazonia – Smoke, Aerosols, Clouds, Rainfall, and Climate) field campaign. Water soluble organic and inorganic compounds in bulk (High Volume and Stacked Filter Unit sampler) and size-resolved (Micro Orifice Uniform Deposit Impactor – MOUDI) smoke samples were determined by ion chromatography. It was found that low molecular weight polar organic acids account for a significant fraction of the water soluble organic carbon (WSOC) in biomass burning aerosols (C2-C6 dicarboxylic acids reached up to 3.7% and one-ring aromatic acids reached up to 2% of fine fraction WSOC during burning period). Short dicarboxylic (C2-C6) acids are dominated by oxalic acid followed by malonic and succinic acids. The largest ionic species is ammonium sulfate (60–70% of ionic mass). It was found that most of the ionic mass is concentrated in submicrometer-sized particles. Based on the size distribution and correlations with K+, a known biomass burning tracer, it is suggested that many of the organic acids are directly emitted by vegetation fires. It is concluded that the dicarboxylic acids are mostly confined to the particulate phase, and no evidence for semi-volatile behavior was observed. Finally, it is shown that the distribution of water soluble species shifts to larger aerosols sizes as the aerosol population ages and mixes with other aerosol types in the atmosphere.
15
Tuason, M. M. S., e J. M. Arocena. "Root organic acid exudates and properties of rhizosphere soils of white spruce (Picea glauca) and subalpine fir (Abies lasiocarpa)". Canadian Journal of Soil Science 89, n. 3 (2 maggio 2009): 287–300. http://dx.doi.org/10.4141/cjss08021.
Testo completoAbstract (sommario):
Rhizosphere processes, such as the production and release of organic acids, contribute to differences in properties between rhizosphere (R) and nonrhizosphere (NR) soils. We compared the organic acid composition/concentrations in the R and NR soil extracts of Picea glauca and Abies lasiocarpa, and in the root exudates of the same tree species. We also evaluated the chemical properties and mineral composition of the soil samples. Higher concentrations of organic acids were observed in R than in NR soils with aliphatic acids predominating in both soil extracts and root exudates. Acetic, formic, and protocatechuic acids were the predominant aliphatic and aromatic organic acids in R and NR soil extracts. Several organic acids in R soil extracts were not detected in NR soil extracts, with the reverse being true as well. Malonic and oxalic acids were predominant in the root exudates of both plant species. The total organic acid concentration was higher in P. glauca than in A. lasiocarpa. Glutaric and isocitric acids were found only in A. lasiocarpa, while gluconic, succinic, and protocatechuic acids were exclusive to P. glauca. Acetic and formic acids were detected in all R soil extracts, but not in root exudates. Glutaric acid (in P. glauca) and gluconic/succinic acids (A. lasiocarpa) were undetectable in root exudates, but were present in the corresponding R soil extracts. Soil pH was lower in the R than NR soil of P. glauca. Cation exchange capacity, and exchangeable Ca2+ and K+ were higher in R than in NR soils except for the A. lasiocarpa LFH horizon. Chlorite, mica, kaolinite, and vermiculite were detected in all soil samples. Smectite was detected more frequently in R than NR soils. Our results suggest that high amounts of organic acids might have played a significant role in the transformation of mica and chlorite into smectite in R soils.Key words: Rhizosphere, root exudates, organic acids
16
Hegde, P., e K. Kawamura. "Seasonal variations of water-soluble organic carbon, dicarboxylic acids, ketocarboxylic acids, and α-dicarbonyls in Central Himalayan aerosols". Atmospheric Chemistry and Physics 12, n. 14 (26 luglio 2012): 6645–65. http://dx.doi.org/10.5194/acp-12-6645-2012.
Testo completoAbstract (sommario):
Abstract. Aerosol samples were collected from a high elevation mountain site (Nainital, India; 1958 m a.s.l.) in the central Himalayas, a location that provides an isolated platform above the planetary boundary layer to better understand the composition of the remote continental troposphere. The samples were analyzed for water-soluble dicarboxylic acids (C2-C12) and related compounds (ketocarboxylic acids and α-dicarbonyls), as well as organic carbon, elemental carbon and water soluble organic carbon. The contributions of total dicarboxylic acids to total aerosol carbon during wintertime were 1.7% and 1.8%, for day and night, respectively whereas they were significantly smaller during summer. Molecular distributions of diacids revealed that oxalic (C2) acid was the most abundant species followed by succinic (C4) and malonic (C3) acids. The average concentrations of total diacids (433±108 ng m−3), ketoacids (48±23 ng m−3), and α-dicarbonyls (9±4 ng m−3) were similar to those from large Asian cities such as Tokyo, Beijing and Hong Kong. During summer most of the organic species were several times more abundant than in winter. Phthalic acid, which originates from oxidation of polycyclic aromatic hydrocarbons such as naphthalene, was found to be 7 times higher in summer than winter. This feature has not been reported before in atmospheric aerosols. Based on molecular distributions and air mass backward trajectories, we conclude that dicarboxylic acids and related compounds in Himalayan aerosols are derived from anthropogenic activities in the highly populated Indo-Gangetic plain areas.
17
Falkovich, A. H., E. R. Graber, G. Schkolnik, Y. Rudich, W. Maenhaut e P. Artaxo. "Low molecular weight organic acids in aerosol particles from Rondônia, Brazil, during the biomass-burning, transition and wet periods". Atmospheric Chemistry and Physics 5, n. 3 (10 marzo 2005): 781–97. http://dx.doi.org/10.5194/acp-5-781-2005.
Testo completoAbstract (sommario):
Abstract. Particles from biomass burning and regional haze were sampled in Rondônia, Brazil, during dry, transition and wet periods from September to November 2002, as part of the LBA-SMOCC (Large-Scale Biosphere-Atmosphere Experiment in Amazonia – Smoke, Aerosols, Clouds, Rainfall, and Climate) field campaign. Water soluble organic and inorganic compounds in bulk (High Volume and Stacked Filter Unit sampler) and size-resolved (Micro Orifice Uniform Deposit Impactor – MOUDI) smoke samples were determined by ion chromatography. It was found that low molecular weight polar organic acids account for a significant fraction of the water soluble organic carbon (WSOC) in biomass burning aerosols (C2-C6 dicarboxylic acids reached up to 3.7% and one-ring aromatic acids reached up to 2% of fine fraction WSOC during burning period). Short dicarboxylic (C2-C6) acids are dominated by oxalic acid followed by malonic and succinic acids. The largest ionic species is ammonium sulfate (60–70% of ionic mass). It was found that most of the ionic mass is concentrated in submicrometer-sized particles. Based on the size distribution and correlations with K+, a known biomass burning tracer, it is suggested that many of the organic acids are directly emitted by vegetation fires. Concentrations of dicarboxylic acids in the front and back filters of high volume sampler were determined. Based on these measurements, it was concluded that in the neutral or slightly basic smoke particles typical of this region, dicarboxylic acids are mostly confined to the particulate phase. Finally, it is shown that the distribution of water soluble species shifts to larger aerosols sizes as the aerosol population ages and mixes with other aerosol types in the atmosphere.
18
Khoury, Dani, Maurice Millet, Yasmine Jabali e Olivier Delhomme. "Phenolic and Acidic Compounds in Radiation Fog at Strasbourg Metropolitan". Atmosphere 15, n. 10 (17 ottobre 2024): 1240. http://dx.doi.org/10.3390/atmos15101240.
Testo completoAbstract (sommario):
Sixty-four phenols grouped as nitrated, bromo, amino, methyl, chloro-phenols, and cresols, and thirty-eight organic acids grouped as mono-carboxylic and dicarboxylic are analyzed in forty-two fog samples collected in the Alsace region between 2015 and 2021 to check their atmospheric behavior. Fogwater samples are collected using the Caltech Active Strand Cloudwater Collector (CASCC2), extracted using liquid–liquid extraction (LLE) on a solid cartridge (XTR Chromabond), and then analyzed using gas chromatography coupled with mass spectrometry (GC-MS). The results show the high capability of phenols and acids to be scavenged by fogwater due to their high solubility. Nitro-phenols and mono-carboxylic acids have the highest contributions to the total phenolic and acidic concentrations, respectively. 2,5-dinitrophenol, 3-methyl-4-nitrophenol, 4-nitrophenol, and 3,4-dinitrophenol have the highest concentration, originating mainly from vehicular emissions and some photochemical reactions. The top three mono-carboxylic acids are hexadecenoic acid (C16), eicosanoic acid (C18), and dodecanoic acid (C12), whereas succinic acid, suberic acid, sebacic acid, and oxalic acid are the most concentrated dicarboxylic acids, originated either from atmospheric oxidation (mainly secondary organic aerosols (SOAs)) or vehicular transport. Pearson’s correlations show positive correlations between organic acids and previously analyzed metals (p < 0.05), between mono- and dicarboxylic acids (p < 0.001), and between the analyzed acidic compounds (p < 0.001), whereas no correlations are observed with previously analyzed inorganic ions. Total phenolic and acidic fractions are found to be much higher than those observed for pesticides, polycyclic aromatic hydrocarbons (PAHs), and polychlorinated biphenyls (PCBs) measured at the same region due to their higher scavenging by fogwater.
19
Ajeel, Zaineb H., e Maha N. Hamad. "Detection and isolation of flavonoid and aromatic acid from Cynara scolymus different parts cultivated in iraq". Iraqi Journal of Pharmaceutical Sciences ( P-ISSN 1683 - 3597 E-ISSN 2521 - 3512) 29, n. 2 (30 dicembre 2020): 202–13. http://dx.doi.org/10.31351/vol29iss2pp202-213.
Testo completoAbstract (sommario):
The target of this study was to study the natural phytochemical components of the head (capsule) of Cynara scolymus cultivated in Iraq. The head (capsule) of plant was extracted by maceration in70% ethanol for 72 hours, and fractioned by hexane, chloroform and ethyl acetate. Preliminary qualitative phytochemical screening was performed on the ethyl acetate fraction for capsule was revealed the presence of flavonoid and aromatic acids. These were examined by (high -performance liquid chromatography) (HPLC diodarray), (high- performance thin-layer chromatography)(HPTLC). Flavonoids were isolated by preparative layer chromatography and aromatic acid was isolated by preparative high-performance liquid chromatography HPLC from the ethyl acetate fraction of capsule. Then identified by High Performance Thin Layer Chromatography HPTLC, High performance liquid chromatography HPLC diode array , ultraviolet diode array UV-diode array and Liquid Chromatography /Mass Spectroscopy LC/MS. The chloroform fraction from the capsule was evaluated by Gas Chromatography//Mass Spectrometer(GC/MS). The different chromatographic and spectroscopic techniques revealed the presence of luteolin, apigenin and cinnamic acid in capsule of Cynara scolymus, also 9-octadecanoic acid (oleic acid), Oxalic acid, allyl tetradecyl ester, limonene, in chloroform of Cynara scolymus. The results of the current study proved the presence of luleolin, apigenin, and cinnamic acid in the ethyl acetate fraction of Cynara scolymus capsule.
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Hegde, P., e K. Kawamura. "Seasonal variations of water-soluble organic carbon, dicarboxylic acids, ketoacids, and α-dicarbonyls in the central Himalayan aerosols". Atmospheric Chemistry and Physics Discussions 12, n. 1 (11 gennaio 2012): 935–82. http://dx.doi.org/10.5194/acpd-12-935-2012.
Testo completoAbstract (sommario):
Abstract. Aerosol samples were collected from a high elevation mountain site (Nainital, India; 1958 m a.s.l.) in the central Himalayas, which provide an isolated platform above the planetary boundary layer to better understand the composition of the remote continental troposphere. The samples were analyzed for water-soluble dicarboxylic acids (C2–C12) and related compounds (ketocarboxylic acids and α-dicarbonyls), as well as organic carbon, elemental carbon and water soluble organic carbon. The contributions of total dicarboxylic acids to total aerosol carbon during wintertime were 1.7 and 1.8%, for day and night, respectively whereas they significantly reduced during summer. Molecular distributions of diacids demonstrated that oxalic (C2) acid was the most abundant species followed by C4 and C3 diacids. The average concentrations of total diacids (433 ± 108 ng m−3), ketoacids (48 ± 23 ng m−3), and α-dicarbonyls (9 ± 4 ng m−3) were similar to those from Asian cities such as Tokyo, Beijing and Hong Kong. During summer season most of the organic species were several times more abundant than in winter. Phthalic acid, which originates from oxidation of polycyclic aromatic hydrocarbons such as naphthalene, was found to be 7 times higher in summer than winter. This feature has not been reported in atmospheric aerosols. Based on molecular distributions and air mass backward trajectories, we report that dicarboxylic acids and related compounds in Himalayan aerosols are influenced by the anthropogenic activities from highly populated Indo-Gangetic plain areas.
21
Zhao, Xuqiang, Li Qin, Michael Gatheru Waigi, Pengfei Cheng, Bing Yang, Jian Wang e Wanting Ling. "Removal of Bound PAH Residues in Contaminated Soils by Fenton Oxidation". Catalysts 9, n. 7 (20 luglio 2019): 619. http://dx.doi.org/10.3390/catal9070619.
Testo completoAbstract (sommario):
The availability of bound residues of polycyclic aromatic hydrocarbons (PAHs), in reference to their parent compounds, can be enhanced by microbial activity and chemical reactions, which pose severe risks for the ecosystems encompassing contaminated soils. Considerable attention has been raised on how to remove these bound residues from PAH-contaminated soils. This paper provides a novel application of Fenton oxidation in the removal of bound residues of model PAHs, such as naphthalene (NAP), acenaphthene (ACP), fluorene (FLU) and anthracene (ANT), from naturally contaminated soils. The citric acid-enhanced Fenton treatment resulted in the degradation of bound PAH residues that followed pseudo-first-order kinetics, with rate constants within 4.22 × 10−2, 1.25 × 10−1 and 2.72 × 10−1 h−1 for NAP, FLU, and ANT, respectively. The reactivity of bound PAH residues showed a correlation with their ionization potential (IP) values. Moreover, the degradation rate of bound PAH residues was significantly correlated with H2O2-Fe2+ ratio (m/m) and H2O2 concentrations. The highest removal efficiencies of bound PAH residues was up to 89.5% with the treatment of chelating agent oxalic acid, which was demonstrated to be superior to other acids, such as citric acid and hydrochloric acid. This study provides valuable insight into the feasibility of citric acid-Fenton and oxalic acid-Fenton treatments in rehabilitating bound PAH residues in contaminated soils.
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Novais, Cláudia, Carla Pereira, Adriana K. Molina, Ângela Liberal, Maria Inês Dias, Mikel Añibarro-Ortega, Maria José Alves, Ricardo C. Calhelha, Isabel C. F. R. Ferreira e Lillian Barros. "Bioactive and Nutritional Potential of Medicinal and Aromatic Plant (MAP) Seasoning Mixtures". Molecules 26, n. 6 (13 marzo 2021): 1587. http://dx.doi.org/10.3390/molecules26061587.
Testo completoAbstract (sommario):
Medicinal and aromatic plants (MAPs), worldwide appreciated and used as condiments, dyes, and preservatives, possess several biological properties that justify their continuous application in the food industry. In the present study, the nutritional and chemical profiles, as well as the bioactive properties of four combinations of condiments, sold for seasoning poultry, meat, fish, and salads, were evaluated. Twenty-five phenolic compounds (HPLC-DAD-ESI/MS) were identified, with apigenin-O-malonyl-pentoside-hexoside as the major compound detected in all extracts. Oxalic and citric acids were identified in all mixtures (UFLC-PDA), as well as all the four tocopherol isoforms (HPLC-fluorescence). Regarding bioactivities, the mixtures for meat and salads (TBARS) and meat and poultry (OxHLIA) stood out for their antioxidant potential, whereas for the anti-inflammatory and antitumor properties, the mixtures revealing the greatest results were those for poultry and salad, respectively. In terms of antimicrobial activity, all the mixtures revealed the capacity to inhibit the growth of some bacterial strains. In brief, condiment mixtures showed to be a good source of bioactive compounds, as they confer health benefits, validating the importance of their inclusion in the human diet as a good dietary practice.
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Liu, Jun Feng, Bai Yan Cui e Yu Jie Feng. "Electrochemical Degradation Pathway of Phenol on Ti/SnO2 Anode". Advanced Materials Research 455-456 (gennaio 2012): 507–12. http://dx.doi.org/10.4028/www.scientific.net/amr.455-456.507.
Testo completoAbstract (sommario):
The electrochemical degradation pathway of phenol, as model organic pollutant, was investigated on antimony doped tin dioxide electrode based on titanium anode (Ti/SnO2). Many intermediates of electrochemical degradation of phenol on Ti/SnO2 were identified and quantified by HPLC. These intermediates were assured as aromatic ring-compounds (hydroquinone, catechol, benzoquinone, et al) and short chain fatty acids (maleic acid, fumaric acid, formic acid, cis muconic acid and 2-oxoglutaric acid, et al). Electrochemical degradation tests were conducted with some intermediates as substrates, including the electrochemical oxidation of formic acid, acetic acid, oxalic acid, malonic acid, acrylic acid, succinic acid, fumaric acid, maleic acid, and 2-oxaglutaric acid, et al. The degradation pathway of phenol on Ti/SnO2 anode was concluded. It is proven that the pathway relates to the element composition on the electrode surface. These findings demonstrate electrochemical degradation of organic pollutants mechanism and help to practical use of catalytic anodes materials.
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Kovaleva, Аlla, Raal Ain, Ilina Tetiana, Alina Osmachko, Olga Goryacha, Ludmila Omelyanchik e Oleh Koshovyi. "Carboxylic acids in the flowers of Veronica spicata L. and Veronica incana L." ScienceRise: Pharmaceutical Science, n. 1(35) (28 febbraio 2022): 37–43. http://dx.doi.org/10.15587/2519-4852.2022.253541.
Testo completoAbstract (sommario):
In the Ukrainian flora, species of Veronica L. genus (Plantaginaceae Juss.) are classified into 8 sections. Among the representatives of Pseudolysimachion W. D. J. Koch section in the Kharkiv region, Veronica spicata L. (spike speedwell) and Veronica incana L. (Veronica spicata L. subsp. incana (L.) Walters, silver speedwell) are common. Plants are used for the treatment of upper respiratory tract diseases, malignant neoplasms, gastrointestinal tract and genitourinary system disorders, diabetes mellitus.
The aim of the research was to study the carboxylic acids of flowers of Veronica spicata L. and Veronica incana L.
Materials and methods. The objects of the research were flowers of Veronica spicata L. and Veronica incana L., collected in the flowering stage in the Botanical Garden of Karazin University (Kharkiv, Ukraine) in summer 2018. The study of carboxylic acid composition was performed by chromatography-mass spectrometry on a 6890N MSD/DS Agilent Technologies chromatograph with a 5973N mass spectrometric detector. Identification of methyl esters of acids was performed using data from the mass spectrum libraries NIST 05 and Willey 2007 in a combination with programs for the identification of AMDIS and NIST; also, their retention time and the retention times of standard compounds were compared.
Results. In Veronica incana L. flowers, 37 carboxylic acids were identified and quantified, constituting 1.05 %. In Veronica spicata L. flowers, 32 carboxylic acids were identified and quantified, the total content of which was 2.75 %.
Conclusions. A higher carboxylic acid content was established in the flowers of Veronica spicata L. The fatty acid composition of Veronica incana L. flowers is characterized by a comparable content of saturated and unsaturated acids, while in Veronica spicata L. flowers, unsaturated fatty acids prevail over saturated fatty acids. The content of aromatic acids in the flowers of studied species was comparable. The characteristic carboxylic acids in the flowers of Veronica incana L. are oxalic, 3-hydroxy-2-methylglutaric, pentadecanoic, heneicosanoic, tricosanic,4-hydroxybenzoic, 4-methoxybenzoic and 3,4-dimethoxybenzoic acids; in the flowers of Veronica spicata L. – 2-hydroxy-3-methylglutaric, α-furanic and homovanillic acids
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Wang, H., Z. Y. Bian e D. Z. Sun. "Degradation mechanism of 4-chlorophenol with electrogenerated hydrogen peroxide on a Pd/C gas-diffusion electrode". Water Science and Technology 63, n. 3 (1 febbraio 2011): 484–90. http://dx.doi.org/10.2166/wst.2011.247.
Testo completoAbstract (sommario):
Using a self-made Pd/C gas-diffusion electrode as the cathode and a Ti/IrO2/RuO2 anode, the degradation of 4-chlorophenol has been investigated in an undivided electrolysis device by the electrochemical oxidation processes. The result indicated that the neutral aqueous solutions can accelerate 4-chlorophenol degradation during electrolysis. The removal efficiency of 4-chlorophenol and COD reached about 89.6% and 62.0% after 120 min electrolysis, respectively. It suggested that most of 4-chlorophenol was oxidised to intermediates using the Pd/C gas-diffusion electrode. Furthermore, the biodegradation ability of the solution was increased significantly during the electrolysis. The degradation of 4-chlorophenol was attributed to the cooperative oxidation processes including electrochemical oxidation at the anode and H2O2 and hydroxyl radical (HO·) produced by the reduction of oxygen at the cathode. Finally, main aromatic intermediates (e.g., hydroquinone and benzoquinone) and main aliphatic carboxylic intermediates (e.g., oxalic, malonic, maleic, succinic, fumaric, and dodecanoic acids) were identified by GC-MS. Moreover, a reaction scheme involving all these intermediates was proposed.
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Tella, M., e G. S. Pokrovski. "Antimony(V) complexing with O-bearing organic ligands in aqueous solution: an X-ray absorption fine structure spectroscopy and potentiometric study". Mineralogical Magazine 72, n. 1 (febbraio 2008): 205–9. http://dx.doi.org/10.1180/minmag.2008.072.1.205.
Testo completoAbstract (sommario):
AbstractThe stabilityand structure of aqueous complexes formed by pentavalent antimony (SbV) with simple organic ligands (acetic, adipic, oxalic, citric acids, catechol and xylitol) having O-functional groups (carboxyl, alcoholic hydroxyl, aliphatic and aromatic hydroxyl) typical of natural organic matter (NOM), were determined at 25°C from potentiometric and X-ray absorption fine structure spectroscopy (XAFS) measurements. In organic-free aqueous solutions, spectroscopic data are consistent with the dominant formation of SbV hydroxide species, Sb(OH)5 and Sb(OH)6-, at acid and near-neutral to basic pH, respectively. Potentiometric measurements demonstrate negligible complexing with mono-functional organic ligands (acetic) or those having non-adjacent carboxylic groups (adipic). In contrast, in the presence of poly-functional carboxylic, hydroxyl carboxylic acids and aliphatic and phenolic hydroxyl, SbV forms stable 1:1 or 1:3 complexes in coordination 6 with the studied organic ligands, over a wide pH range pertinent to natural waters (3 ≤ pH ≤ 9). The XAFS measurements show that in these species the central SbV atom has an octahedral geometry with 6 oxygen atoms from hydroxyl moieties and adjacent functional groups (O = C—OH and/or C—OH) of the ligand, forming bidendate chelate cycles. Stability constants for SbV-oxalate complexes generated from potentiometric experiments were used to model SbV complexing with di-carboxylic functional groups of natural humic acids. Our predictions show that in an aqueous solution of pH between 1 and 4 containing 1 μg/l of Sb and 5 mg/l of dissolved organic carbon (DOC), up to 15% of total dissolved Sb maybe bound to aqueous organic matter via di-carboxylic groups.
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Ho, K. F., S. S. H. Ho, S. C. Lee, K. Kawamura, S. C. Zou, J. J. Cao e H. M. Xu. "Summer and winter variations of dicarboxylic acids, fatty acids and benzoic acid in PM<sub>2.5</sub> in Pearl Delta River Region, China". Atmospheric Chemistry and Physics 11, n. 5 (11 marzo 2011): 2197–208. http://dx.doi.org/10.5194/acp-11-2197-2011.
Testo completoAbstract (sommario):
Abstract. Ground-based PM2.5 samples collected at four different sites in Pearl River Delta region (PRD) during winter and summer (from 14 December 2006 to 28 January 2007 in winter and from 4 July to 9 August 2007 in summer) were analyzed for 30 water-soluble organic species, including dicarboxylic acids, ketocarboxylic acids and dicarbonyls, nine fatty acids, and benzoic acid. Molecular distributions of dicarboxylic acids demonstrated that oxalic acid (C2) was the most abundant species followed by phthalic acid (Ph) in PRD region. The concentrations of total dicarboxylic acids ranged from 99 to 1340 ng m−3, with an average of 438 ± 267 ng m−3 in PRD. The concentrations of total ketocarboxylic acids ranged from 0.6 to 207 ng m−3 (43 ± 48 ng m−3 on average) while the concentrations of total α-dicarbonyls, including glyoxal and methylglyoxal, ranged from 0.2 to 89 ng m−3, with an average of 11 ± 18 ng m−3 in PRD. The total quantified water-soluble compounds (TQWOC) (organic carbon) accounted for 3.4 ± 2.2% of OC and 14.3 ± 10.3% of water-soluble OC (WSOC). Hexadecanoic acid (C16:0), octadecanoic acid (C18:0) and oleic acid (C18:1) were the three most abundant fatty acids in PRD. The distributions of fatty acids were characterized by a strong even carbon number predominance with a maximum (Cmax) at hexadecanoic acid (C16:0). Ratio of C18:1 to C18:0 acts as an indicator for aerosol aging. In PRD, an average of C18:1/C18:0 ratio was 0.53 ± 0.39, suggesting an enhanced photochemical degradation of unsaturated fatty acid. Moreover, the concentrations of benzoic acid ranged from 84 to 306 ng m−3, (165 ± 48 ng m−3 on average), which can be emitted as primary pollutant from motor vehicles exhaust, or formed from photochemical degradation of aromatic hydrocarbons. Seasonal variations of the organic specie concentrations were found in the four sampling cities. Higher concentrations of TQWOC were observed in winter (598 ± 321 ng m−3) than in summer (372 ± 215 ng m−3). However, the abundances of TQWOC in OC mass were higher in summer (0.9–12.4%, 4.5 ± 2.7% on average) than in winter (1.1–5.7, 2.5 ± 1.2% on average), being consistent with enhanced secondary production of dicarboxylic acids in warmer weather. Spatial variations of water-soluble dicarboxylic acids were characterized by higher concentrations in Hong Kong and lower concentrations in Guangzhou (GZ)/Zhaoqing (ZQ) during winter whereas the highest concentrations were observed in GZ/ZQ during summer. These spatial and seasonal distributions are consistent with photochemical production and the subsequent accumulation under different meteorological conditions.
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Kawamura, K., E. Tachibana, K. Okuzawa, S. G. Aggarwal, Y. Kanaya e Z. F. Wang. "High abundances of water-soluble dicarboxylic acids, ketocarboxylic acids and α-dicarbonyls in the mountaintop aerosols over the North China Plain during wheat burning season". Atmospheric Chemistry and Physics 13, n. 16 (22 agosto 2013): 8285–302. http://dx.doi.org/10.5194/acp-13-8285-2013.
Testo completoAbstract (sommario):
Abstract. Aerosol (TSP) samples were collected at the summit of Mount Tai (elevation: 1534 m a.s.l., 36.25° N, 117.10° E) located in the North China Plain using a high-volume air sampler and pre-combusted quartz filters. Sampling was conducted on day/night or 3 h basis in the period from 29 May to 28 June 2006 during the field burning of wheat straw residue and the post-burning season. The filter samples were analyzed for low-molecular-weight dicarboxylic acids, ketoacids and α-dicarbonyls using capillary gas chromatography (GC) and GC-MS employing water extraction and butyl ester derivatization. Molecular distributions of dicarboxylic acids (C2-C11, 220–6070 ng m−3) were characterized by a predominance of oxalic (C2) acid (105–3920 ng m−3) followed by succinic (C4) or malonic (C3) acid. Unsaturated aliphatic diacids, including maleic (M), isomaleic (iM) and fumaric (F) acids, were also detected together with aromatic diacids (phthalic, isophthalic and terephthalic acids). ω-oxocarboxylic acids (C2-C9, 24–610 ng m−3) were detected as the second most abundant compound class with the predominance of glyoxylic acid (11–360 ng m−3), followed by α-ketoacid (pyruvic acid, 3–140 ng m−3) and α-dicarbonyls (glyoxal, 1–230 ng m−3 and methylglyoxal, 2–120 ng m−3). We found that these levels (>6000 ng m−3 for diacids) are several times higher than those reported in Chinese megacities at ground levels. The concentrations of diacids increased from late May to early June, showing a maximum on 7 June, and then significantly decreased during the period 8–11 June, when the wind direction shifted from southerly to northerly. Similar temporal trends were found for ketocarboxylic acids and α-dicarbonyls as well as total carbon (TC) and water-soluble organic carbon (WSOC). The temporal variations of water-soluble organics were interpreted by the direct emission from the field burning of agricultural wastes (wheat straw) in the North China Plain and the subsequent photochemical oxidation of volatile and semi-volatile organic precursors emitted from field burning as well as dark ozonolysis of volatile organic compounds and other organics, accretion reactions and oxidation of nonvolatile organics such as unsaturated fatty acids. This study demonstrates that the field burning of agricultural wastes in early summer strongly influenced the air quality of the free troposphere over the North China Plain.
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Kawamura, K., E. Tachibana, K. Okuzawa, S. G. Aggarwal, Y. Kanaya e Z. F. Wang. "High abundances of water-soluble dicarboxylic acids, ketocarboxylic acids and α-dicarbonyls in the mountain aerosols over the North China Plain during wheat burning season". Atmospheric Chemistry and Physics Discussions 13, n. 2 (8 febbraio 2013): 3695–734. http://dx.doi.org/10.5194/acpd-13-3695-2013.
Testo completoAbstract (sommario):
Abstract. Aerosol (TSP) samples were collected at the summit of Mount Tai (elevation: 1534 m a.s.l., 36.25° N; 117.10° E) located in the North China Plain using a high-volume air sampler and pre-combusted quartz filters. Sampling was conducted on day/night or 3 h basis in the period from 29 May to 28 June 2006 during the field burning of wheat straw residue and the post-burning season. The filter samples were analyzed for low molecular weight dicarboxylic acids, ketoacids and α-dicarbonyls using capillary gas chromatography (GC) and GC-MS employing water extraction and butyl ester derivatization. Dicarboxylic acids (C2–C11, 220–6070 ng m−3) were characterized by a predominance of oxalic (C2) acid (105–3920 ng m−3) followed by succinic (C4) or malonic (C3) acid. Unsaturated aliphatic diacids, including maleic (M), isomaleic (iM) and fumaric (F) acid, were also detected together with aromatic diacids (phthalic, iso-phthalic and tere-phthalic acids). ω-Oxocarboxylic acids (C2–C9, 24–610 ng m−3) were detected as the second most abundant compound class with the predominance of glyoxylic acid (11–360 ng m−3), followed by α-ketoacid (pyruvic acid, 3–140 ng m−3) and α-dicarbonyls (glyoxal, 1–230 ng m−3 and methylglyoxal, 2–120 ng m−3). We found that these levels (> 6000 ng m−3 for diacids) are several times higher than those reported in Chinese megacities at ground levels. The concentrations of diacids increased from late May to early June showing a maximum on 7 June and then significantly decreased during 8–11 June when the wind direction shifted from northeasterly to northerly. Similar temporal trends were found for ketocarboxylic acids and α-dicarbonyls as well as total carbon (TC) and water-soluble organic carbon (WSOC). The temporal variations of water-soluble organics were interpreted by the direct emission from the field burning products of agricultural wastes (wheat straw) in the North China Plain and the subsequent photochemical oxidation of volatile and semi-volatile organic precursors emitted from field burning. This study demonstrates that the field burning of agricultural wastes in early summer strongly influenced the air quality of the free troposphere over the North China Plain.
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Bensalah, Nasr, Mohammad I. Ahmad e Ahmed Bedoui. "Catalytic Degradation of 4-Ethylpyridine in Water by Heterogeneous Photo-Fenton Process". Applied Sciences 9, n. 23 (25 novembre 2019): 5073. http://dx.doi.org/10.3390/app9235073.
Testo completoAbstract (sommario):
In this work, the degradation of 4-ethylpyridine (4EP) in water by a heterogeneous photo-Fenton process (H2O2/Fe3O4/ultraviolet irradiation (UV)) was investigated. More rapid and effective 4EP degradation was obtained with H2O2/Fe3O4/UV than Fenton-like (H2O2/Fe3O4) and UV/H2O2, which is due to the larger production of hydroxyl radicals from the chemical and photolytic decomposition of H2O2. The operational conditions were varied during 4EP degradation experiments to evaluate the effects of pH, catalyst, concentration, and temperature on the kinetics and efficiency of H2O2/Fe3O4/UV oxidation. Under optimal conditions (100 mg/L 4EP, [H2O2] = 1000 mg/L, Fe3O4 = 40 mg/L, pH = 3 and room temperature, 300 rpm), 4EP was totally declined and more than 93% of the total organic carbon (TOC) was eliminated. Liquid chromatography analysis confirmed the formation of aromatic and aliphatic intermediates (4-hydroxypyridine, 4-pyridone, malonic, oxalic, and formic acids) that resulted in being mineralized. Ion chromatography analysis demonstrated the stoichiometric release of NH4+ ions during 4EP degradation by heterogeneous photo-Fenton oxidation. The reuse of the heterogeneous catalyst was evaluated after chemical and heat treatment at different temperatures. The heat-treated catalyst at 500 °C presented similar activity than the pristine Fe3O4. Accordingly, heterogeneous photo-Fenton oxidation can be an alternative method to treat wastewaters and groundwater contaminated with pyridine derivatives and other organic micropollutants. The combination of heterogeneous photo-Fenton oxidation with classical biological methods can be proposed to reduce the overall cost of the treatment in large-scale water treatment plants.
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He, N., K. Kawamura, K. Okuzawa, Y. Kanaya e Z. F. Wang. "Diurnal variations of total carbon, dicarboxylic acids, ketoacids and α-dicarbonyls in aerosols in the northern vicinity of Beijing". Atmospheric Chemistry and Physics Discussions 13, n. 6 (21 giugno 2013): 16699–731. http://dx.doi.org/10.5194/acpd-13-16699-2013.
Testo completoAbstract (sommario):
Abstract. Aerosol samples (TSP, n=58) were collected on day- and night-time basis at Mangshan in the north of Beijing, China in autumn 2007 to better understand the status of air quality and the influence of urban pollutants in the northern vicinity of Beijing. The samples were analyzed for aerosol mass, total carbon (TC), low molecular weight α, ω-dicarboxylic acids (C2-C12), ketoacids (ωC2-ωC9, pyruvic acid), α-dicarbonyls (glyoxal and methylglyoxal), as well as aromatic (phthalic, iso- and tere-phthalic) diacids. Aerosol mass and TC concentrations are higher in daytime than in nighttime. TC/aerosol mass ratios in this study are lower than those reported in megacities in East Asia, but higher than those reported in marine aerosols. Molecular distributions of diacids demonstrated that oxalic (C2) acid was the most abundant species, comprising 38–77% of total diacids, followed by succinic (C4) and malonic (C3) acids. For most compounds, the concentrations were higher in daytime than nighttime, indicating that diacids are produced in daytime by photochemical oxidation of organic precursors emitted from anthropogenic sources in Beijing during the transport to Mangshan area by the northward wind. However, we found that C2 concentrations are higher in nighttime than in daytime. A positive correlation of C2 to glyoxylic acid (ωC2) was obtained at night when relative humidity increased up to 100%, suggesting that aqueous phase production of C2 occurs in nighttime via the oxidation of ωC2. Depletion of C2 by photolysis of Fe-oxalato complexes might be another reason for the lower concentrations of C2 in daytime samples. High phthalic acid/C4 ratios in the aerosol samples suggest that automobile combustion and coal burning products are important sources, which are subjected to photochemical oxidation during the atmospheric transport of urban aerosols from Beijing. In contrast, higher concentrations of methylglyoxal in nighttime than daytime may suggest that isoprene emitted from the northern forest area is oxidized in daytime and then transported to the sampling area at night by northerly winds. This study demonstrates that secondary organic aerosols are significantly produced and aged in the vicinity of Beijing during atmospheric transport.
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Wang, G., M. Xie, S. Hu, E. Tachibana e K. Kawamura. "Dicarboxylic acids, metals and isotopic compositions of C and N in atmospheric aerosols from inland China: implications for dust and coal burning emission and secondary aerosol formation". Atmospheric Chemistry and Physics Discussions 10, n. 3 (11 marzo 2010): 6895–921. http://dx.doi.org/10.5194/acpd-10-6895-2010.
Testo completoAbstract (sommario):
Abstract. Dicarboxylic acids (C2-C10), metals, elemental carbon (EC), organic carbon (OC), and stable isotopic compositions of total carbon (TC) and total nitrogen (TN) were determined for PM10 samples collected at three urban and one suburban sites of Baoji, an inland city of China, during winter and spring 2008. Oxalic acid (C2) was the dominant diacid, followed by succinic (C4) and malonic (C3) acids. Total diacids in the urban and suburban areas are 1546±203 and 1728±495 ng m−3 during winter and 1236±335 and 1028±193 ng m−3 during spring. EC in the urban and the suburban atmospheres are 17±3.8 and 8.0±2.1 μg m−3 during winter and 20±5.9 and 7.1±2.7 μg m−3 during spring whereas OC at the urban and suburban sites are 74±14 and 51±7.9 μg m−3 in winter and 51±20 and 23±6.1 μg m−3 in spring. Secondary organic carbon (SOC) accounted for 38±16% of OC in winter and 28±18% of OC in spring, suggesting an enhanced photochemical production of secondary organic aerosols in winter under an inversion layer development. Total metal elements in winter and spring are 34±10 and 61±27 μg m−3 in the urban air and 18±7 and 32±23 μg m−3 in the suburban air. A linear correlation (r2>0.8 in winter and r2>0.6 in spring) was found between primary organic carbon (POC) and Ca2+/Fe, together with a strong dependence of pH value on water-soluble inorganic carbon, suggesting fugitive dust as a major source of the airborne particles. Polycyclic aromatic hydrocarbons (PAHs), sulfate, and Pb in the samples well correlated each other (r2>0.6) in winter samples, suggesting an importance of emissions from coal burning for house heating. Stable carbon isotope compositions of TC (δ13C) became higher with an increase in the concentration ratios of C2/OC due to aerosol aging. In contrast, nitrogen isotope compositions of TN (δ15N) became lower with an increases in the mass ratios of NH4+/PM10 and NO3-/PM10 due to an enhanced adsorption and/or condensation of NH3 and HNO3 from gas phase onto solid phase.
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Wang, G., M. Xie, S. Hu, S. Gao, E. Tachibana e K. Kawamura. "Dicarboxylic acids, metals and isotopic compositions of C and N in atmospheric aerosols from inland China: implications for dust and coal burning emission and secondary aerosol formation". Atmospheric Chemistry and Physics 10, n. 13 (6 luglio 2010): 6087–96. http://dx.doi.org/10.5194/acp-10-6087-2010.
Testo completoAbstract (sommario):
Abstract. Dicarboxylic acids (C2–C10), metals, elemental carbon (EC), organic carbon (OC), and stable isotopic compositions of total carbon (TC) and total nitrogen (TN) were determined for PM10 samples collected at three urban and one suburban sites of Baoji, an inland city of China, during winter and spring 2008. Oxalic acid (C2) was the dominant diacid, followed by succinic (C4) and malonic (C3) acids. Total diacids in the urban and suburban areas were 1546±203 and 1728±495 ng m−3 during winter and 1236±335 and 1028±193 ng m−3 during spring. EC in the urban and the suburban atmospheres were 17±3.8 and 8.0±2.1 μg m−3 during winter and 20±5.9 and 7.1±2.7 μg m−3 during spring, while OC at the urban and suburban sites were 74±14 and 51±7.9 μg m−3 in winter and 51±20 and 23±6.1 μg m−3 in spring. Secondary organic carbon (SOC) accounted for 38±16% of OC in winter and 28±18% of OC in spring, suggesting an enhanced photochemical production of secondary organic aerosols in winter under an inversion layer development. Total metal elements in winter and spring were 34±10 and 61±27 μg m−3 in the urban air and 18±7 and 32±23 μg m−3 in the suburban air. A linear correlation (r2>0.8 in winter and r2>0.6 in spring) was found between primary organic carbon (POC) and Ca2+/Fe, together with a strong dependence of pH value of sample extracts on water-soluble inorganic carbon, suggesting fugitive dust as an important source of the airborne particles. Polycyclic aromatic hydrocarbons (PAHs), sulfate, and Pb in the samples well correlated each other (r2>0.6) in winter, indicating an importance of emissions from coal burning for house heating. Stable carbon isotope compositions of TC (δ13C) became higher with an increase in the concentration ratios of C2/OC due to aerosol aging. In contrast, nitrogen isotope compositions of TN (δ15N) became lower with an increases in the mass ratios of NH4+/PM10 and NO3−/PM10, which is possibly caused by an enhanced adsorption and/or condensation of gaseous NH3 and HNO3 onto particles.
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Smith, Graham, e Daniel E. Lynch. "Cyclic heterotetrameric and low-dimensional hydrogen-bonded polymeric structures in the morpholinium salts of ring-substituted benzoic acid analogues". Acta Crystallographica Section C Structural Chemistry 72, n. 2 (14 gennaio 2016): 105–11. http://dx.doi.org/10.1107/s2053229615024821.
Testo completoAbstract (sommario):
The morpholinium (tetrahydro-2H-1,4-oxazin-4-ium) cation has been used as a counter-ion in both inorganic and organic salt formation and particularly in metal complex stabilization. To examine the influence of interactive substituent groups in the aromatic rings of benzoic acids upon secondary structure generation, the anhydrous salts of morpholine with salicylic acid, C4H10NO+·C7H5O3−, (I), 3,5-dinitrosalicylic acid, C4H10NO+·C7H3N2O7−, (II), 3,5-dinitrobenzoic acid, C4H10NO+·C7H3N2O6−, (III), and 4-nitroanthranilic acid, C4H10NO+·C7H5N2O4−, (IV), have been prepared and their hydrogen-bonded crystal structures are described. In the crystal structures of (I), (III) and (IV), the cations and anions are linked by moderately strong N—H...Ocarboxylhydrogen bonds, but the secondary structure propagation differs among the three,viz.one-dimensional chains extending along [010] in (I), a discrete cyclic heterotetramer in (III), and in (IV), a heterotetramer with amine N—H...O hydrogen-bond extensions alongb, giving a two-layered ribbon structure. With the heterotetramers in both (III) and (IV), the ion pairs are linked though inversion-related N—H...Ocarboxylatehydrogen bonds, giving cyclicR44(12) motifs. With (II), in which the anion is a phenolate rather than a carboxylate, the stronger assocation is through a symmetric lateral three-centre cyclicR12(6) N—H...(O,O′) hydrogen-bonding linkage involving the phenolate and nitro O-atom acceptors of the anion, with extension through a weaker O—H...Ocarboxylhydrogen bond. This results in a one-dimensional chain structure extending along [100]. In the structures of two of the salts [i.e.(II) and (IV)], there are also π–π ring interactions, with ring-centroid separations of 3.5516 (9) and 3.7700 (9) Å in (II), and 3.7340 (9) Å in (IV).
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Das, Suven, e Arpita Dutta. "Silver‐Catalyzed Decarboxylative Radical Cyclizations: Developments and Insights". Asian Journal of Organic Chemistry, 12 giugno 2024. http://dx.doi.org/10.1002/ajoc.202400225.
Testo completoAbstract (sommario):
Transition‐metal‐catalyzed decarboxylative cross‐coupling reaction provides a powerful method for the construction C‐C, C‐N, C‐O bonds, which have great impact on synthetic chemistry. The use of silver salts as catalyst in decarboxylative reaction gradually increases because of their easy availability, low toxicity, biocompatibility and adequate stability. In fact, various radical cyclization reactions have been accomplished by exploiting single electron transfer (SET) ability of silver salts. The present review highlights recent advances (2015‐mid 2023) in the silver‐catalyzed decarboxylative radical cyclizations for the construction of cyclic molecular scaffolds. The content of the review is organized on the basis of decarboxylative reagents, such as, α‐keto acids, aliphatic/aromatic carboxylic acids, α,α‐difluoroacetic acids, amino acids, alkynyl carboxylic acids, oxamic acids and miscellaneous acids. Additionally, mechanistic insights of most of the reactions are highlighted for well understanding of the reaction mode.
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Sakai, Norio, Kohei Minato, Shota Nakata e Yohei Ogiwara. "Synthesis of Dibenzotetrathiafulvalenes of Oxalic Acid with Electron-Rich Aromatic 1,2-Dithiols and Application to Dithioacetalization with 9-Fluorenecarboxylic Acids or Dicarboxylic Acids". Synthesis, 17 gennaio 2022. http://dx.doi.org/10.1055/a-1742-2821.
Testo completoAbstract (sommario):
AbstractWe have developed a two-step synthesis of dibenzotetrathiafulvalene (DBTTF) derivatives by combining the indium-catalyzed reductive dithioacetalization of oxalic acid and electron-rich aromatic dithiols with a subsequent oxidation of the resultant dithioacetals. The same transformation of electron-rich aromatic dithiols with either 9-fluorenecarboxylic acid derivatives or dicarboxylic acids effectively produced the corresponding benzo-1,3-dithiafulvene derivatives.
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Marchyshyn, S. M., M. I. Shanayda, I. Z. Kernychna, O. L. Demydiak, I. S. Dahym, T. S. Berdey e I. M. Potishnyj. "QUALITATIVE COMPOSITION AND ORGANI C ACIDS CONTENT IN THE ABOVEGROUN D PART OF PLANTS FRO M FAMILIES LAMIACEAE, ASTERACEAE, APIACEAE AND CHENOPODIACEAE". International Journal of Medicine and Medical Research, n. 1 (12 maggio 2016). http://dx.doi.org/10.11603/ijmmr.2413-6077.2015.2.6374.
Testo completoAbstract (sommario):
<p>Background. Organic acids are the compounds of aliphatic or aromatic orders, which are widespread in<br />flora and have a wide range of biological activity. We studied the qualitative composition and quantitative contents<br />of organic acids in the aboveground part of some unofficial medicinal plants from families Lamiaceae, Asteraceae,<br />Apiaceae and Chenopodiaceae is relevant.<br />Objective. The objects of the research are the aboveground part of unofficial medicinal plants from families<br />Lamiaceae, Asteraceae, Apiaceae and Chenopodiaceae.<br />Methods. Identification of organic acids was performed by means of thin-layer and paper chromatography,<br />their content was determined by means of gas chromatography, the quantitative amount of organic acids was<br />defined by titrimetric analysis.<br />Results. In the studied raw plants the quality of organic acids and their total contents were determined (in<br />terms of malic acid). It is established that the maximum content of organic acids is accumulated in the grass<br />Hyssopus officinalis L. (Lamiaceae), and the minimal is in the leaves of Chrysánthemum xhortorum L. variety Apro<br />(Asteraceae). In all studied raw plants the dominance of aliphatic acids (citric, malic, oxalic and malonic) was<br />determined by means of gas chromatography. Benzoic is predominant among the aromatic acids.<br />Conclusions. In the studied raw plants the quality of organic acids and their total content were determined.<br />The following results can be used in developing the methods of quality control of the studied raw plants and<br />during the study of new bioactive substances.<br />KEY WORDS: organic acids, Lamiaceae, Asteraceae, Apiaceae, Сhenopodiaceae, grass, leaves, thinlayer<br />chromatography, gas chromatography, paper chromatography.</p>
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Sakai, Norio, Kohei Minato, Shota Nakata e Yohei Ogiwara. "Synthesis of Dibenzotetrathiafulvalenes of Oxalic Acid with Electron-Rich Aromatic 1,2-Dithiols and Application to Dithioacetalization with 9-Fluorenecarboxylic Acids or Dicarboxylic Acids". Synthesis, 24 marzo 2022. http://dx.doi.org/10.1055/s-0041-1737565.
Testo completo
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Villota, Natalia, Federico Mijangos, Fernando Varona e Javier Andrés. "Kinetic Modelling of Toxic Compounds Generated during Phenol Elimination in Wastewaters". International Journal of Chemical Reactor Engineering 5, n. 1 (1 ottobre 2007). http://dx.doi.org/10.2202/1542-6580.1541.
Testo completoAbstract (sommario):
This work focuses on the application of Advanced Oxidation Processes (AOPs) to purify phenolic effluents, which when combined with innovation and effectiveness contribute towards the preservation of natural resources and environmental quality. Phenols are typical pollutants found in wastewaters from different industries such as petrochemical, pharmaceutical, resin manufacturing, olive-oil, pesticides, dyeing production or cosmetic industry. Nevertheless due to their toxicity and harmfulness, they cannot be poured to water systems. Phenol has been chosen as a model compound in this study because it is usually a component of industrial wastewaters. Furthermore phenol-like compounds are generated by intermediate compounds in the oxidation pathway of higher molecular weight aromatic hydrocarbons.Phenol can be effectively removed but this does not imply that the all toxicity levels of the effluent have been diminished, since the oxidation pathway passes through more toxic products. Before each AOP application, the reaction intermediates must be identified in order to determine the influence they have on operating conditions, and subsequently establish the criteria for the complete destruction of toxic compounds. These studies will assist in the cost-effective operation of industrial setups, and also in the design of integrated processes for wastewater treatment.The main objectives of this work are, first to identify and measure toxic intermediates and, second, to develop a kinetic model for phenol degradation based on a mechanism in series. Chemical pathways in the phenol oxidation consider its hydroxylation to catechol, hydroquinone and resorcinol. These dihydroxylated rings are later oxidised to quinone-like compounds. These quinone-like compounds break into short-chain acids, like acetic, formic and oxalic acids. In order to propose a reaction pathway several runs were carried out at room temperature controlling the operational pH throughout the reaction. Experiments were carried out under different operating conditions, and the decay curves of phenol and aromatic intermediates were monitored, using doses of oxidant and catalyst until R=40 mol oxidant/mol phenol and [Fe(II)]=20 mg/L. Kinetic parameters were rightly fitted to the kinetic model, predicting successfully the reaction rates of each toxic compounds.
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Ferreiro, Cristian, Josu Sanz, Natalia Villota, Ana de Luis e José Ignacio Lombraña. "Kinetic modelling for concentration and toxicity changes during the oxidation of 4-chlorophenol by UV/H2O2". Scientific Reports 11, n. 1 (3 agosto 2021). http://dx.doi.org/10.1038/s41598-021-95083-7.
Testo completoAbstract (sommario):
AbstractThis work develops a kinetic model that allow to predict the water toxicity and the main degradation products concentration of aqueous solutions containing 4-chlorophenol oxidised by UV/H2O2. The kinetic model was developed grouping degradation products of similar toxicological nature: aromatics (hydroquinone, benzoquinone, 4-chlorocatechol and catechol), aliphatics (succinic, fumaric, maleic and malonic acids) and mineralised compounds (oxalic, acetic and formic acids). The degradation of each group versus time was described as a mathematical function of the rate constant of a second-order reaction involving the hydroxyl radical, the quantum yield of lump, the concentration of the hydroxyl radicals and the intensity of the emitted UV radiation. The photolytic and kinetic parameters characterising each lump were adjusted by experimental assays. The kinetic, mass balance and toxicity equations were solved using the Berkeley Madonna numerical calculation tool. Results showed that 4-chlorophenol would be completely removed during the first hour of the reaction, operating with oxidant molar ratios higher than R = 200 at pH 6.0 and UV = 24 W. Under these conditions, a decrease in the rate of total organic carbon (TOC) removal close to 50% from the initial value was observed. The solution colour, attributed to the presence of oxidation products as p-benzoquinone and hydroquinone, were oxidised to colourless species, that resulted in a decrease in the toxicity of the solutions (9.95 TU) and the aromaticity lost.
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Dutta, Arup Kumar, Ruli Borah e Kabita Boruah. "Development of N,N-disulfo-1,1,3,3-tetramethylguanidinium chlorometallates as heterogeneous catalysts for one pot synthesis of 1,2-dihydro-1-aryl-3H-naphth[1, 2-e][1,3]oxazin-3-one derivatives". Current Organocatalysis 07 (21 luglio 2020). http://dx.doi.org/10.2174/2213337207999200721012534.
Testo completoAbstract (sommario):
Background: Four members of N,N-disulfo-1,1,3,3-tetramethylguanidinium chlorometallates [DSTMG]n[X], where n= 1 or 2; X= FeCl4 - , Zn2Cl6 2-, NiCl4 2-, MnCl4 2- were synthesized as solid Brønsted-Lewis acidic compounds and studied the catalytic activity with the most acidic salt for three-component synthesis of 1,2-dihydro-1-aryl-3H-naphth[1,2- e][1,3]oxazin-3-ones. Methods: N,N-disulfo-1,1,3,3-tetramethylguanidinium chlorometallates of the four transition metal cations such as Fe(III), Zn(II), Ni(II) and Mn(II) were prepared after treatment of the parent ionic liquid N,N-disulfo-1,1,3,3- tetramethylguanidinium chloride [DSTMG][Cl] with the respective metal chlorides in different mole fractions at 75 ºC. The synthesis of 1,2-dihydro-1-aryl-3H-naphth[1,2-e][1,3]oxazin-3-ones was carried out via three-component reaction of 2-naphthol, aromatic aldehydes and urea under neat condition at 90 ºC using 7 mol% of the [DSTMG][FeCl4] catalyst. Results: The characterization of synthesized chlorometallates were done using spectroscopic and other analytical techniques including thermogravimetric analysis and Hammett acidity studies. Among the four salts, the salt of Fe(III) ion was observed as the strong Brønsted acidic hydrophobic salt and thus chosen for the catalytic study. Conclusion: A new type of chlorometallates of guanidinium cation with composition [DSTMG]n[X], where X= FeCl4 - /Zn2Cl6 2-/ NiCl4 2-/ MnCl4 2- and n= 1 or 2 were developed as –SO3H functionalized solid acids with varied thermal stability (150-250 ºC) and physisorbed water (0-20%) as observed from the thermogravimetric study. From them, the most Brønsted acidic Fe(III) salt was employed as efficient recyclable heterogeneous catalyst for the one-pot synthesis of 1,2- dihydro-1-aryl-3H-naphth[1,2-e][1,3]oxazin-3-ones in neat condition.