Literatura científica selecionada sobre o tema "Aromatic oxamic acids"
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Artigos de revistas sobre o assunto "Aromatic oxamic acids"
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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.º 1 (6 de dezembro de 2010): 27–37. http://dx.doi.org/10.1135/cccc2010111.
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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.
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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.º 4 (abril de 2009): 683–89. http://dx.doi.org/10.1139/s08-054.
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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.
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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.º 3 (1 de agosto de 1993): 293–98. http://dx.doi.org/10.4141/cjss93-031.
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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
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Shanaida, Mariia, e Alina Holenko. "CHROMATOGRAPHIC ANALYSIS OF CARBOXYLIC ACIDS IN THE FLOWERING SHOOTS OF SOME Vitex L. SPECIES". Acta Medica Leopoliensia 28, n.º 1-2 (30 de junho de 2022): 99–103. http://dx.doi.org/10.25040/aml2022.1-2.099.
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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.
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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.º 3 (março de 2012): 123–26. http://dx.doi.org/10.3184/174751912x13285455672357.
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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.
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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.º 4 (26 de julho de 2018): 306–15. http://dx.doi.org/10.1515/gps-2017-0056.
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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.
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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.º 1 (6 de fevereiro de 2002): 32–38. http://dx.doi.org/10.1515/hf.2002.006.
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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).
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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.º 11 (29 de maio de 2023): 4408. http://dx.doi.org/10.3390/molecules28114408.
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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.
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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 de outubro de 2019): 1–9. http://dx.doi.org/10.1155/2019/7653154.
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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.
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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.º 19 (1 de outubro de 2019): 3555. http://dx.doi.org/10.3390/molecules24193555.
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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.
Teses / dissertações sobre o assunto "Aromatic oxamic acids"
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Badufle, Margaux. "Nouvelle méthode pour la synthèse d'acides N-aryloxamiques et applications". Electronic Thesis or Diss., Bordeaux, 2024. http://www.theses.fr/2024BORD0365.
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Ce manuscrit présente un nouveau procédé de synthèse d’acides oxamiques aromatiques et leur utilisation en tant que précurseurs de radicaux carbamoyles, pour promouvoir une chimie plus verte et plus sûre des isocyanates. La première étape de ce procédé consiste en une réaction de couplage croisé d’Ullmann-Goldberg entre un iodure d’aryle et un oxamate primaire. Son optimisation a mis en évidence l’influence significative du substituant de l’oxamate sur le rendement de la réaction, et différents modes de désactivation du catalyseur. Un grand nombre d’oxamates aromatiques ont ainsi été synthétisés, et plusieurs bis(oxamates) ont été obtenus, élargissant les possibilités d'utilisation de cette méthode pour la synthèse de polymères. Ensuite, quelques-uns de ces oxamates ont été déprotégés en milieu acide pour former les acides oxamiques correspondants. Par une décarboxylation oxydante en conditions thermiques ou photocatalytiques, ces derniers ont enfin été utilisés comme précurseurs de radicaux carbamoyles dans le cadre de deux applications : la génération in situ d’isocyanates par leur oxydation pour la synthèse d’uréthanes, et leur addition sur des imines pour la synthèse d’amides d’α-aminoacidesThis manuscript describes a new process for the synthesis of aromatic oxamic acids and their use as carbamoyl radical precursors, aiming to promote a greener and safer chemistry of isocyanates. The first step of this synthesis consists in an Ullmann-Goldberg cross-coupling reaction between an aryl iodide and a primary oxamate. Its optimization highlighted the significant influence of the oxamate substituent on the reaction yield, and the different modes of catalyst deactivation. A large number of aromatic oxamates were synthesized, and several bis(oxamates) were obtained, expanding the potential use of this method for polymer synthesis. Subsequently, some of these oxamates were deprotected under acidic conditions to obtain corresponding oxamic acids. Through oxidative decarboxylation under thermal or photocatalytic conditions, the latter were finally used as carbamoyl radical precursors for two applications : the in situ generation of isocyanates through their oxidation for urethanes synthesis, and their addition to imines for the synthesis of α-aminoacid amides
Capítulos de livros sobre o assunto "Aromatic oxamic acids"
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Coppens, Philip. "Electron Density Studies of Molecular Crystals". In X-Ray Charge Densities and Chemical Bonding. Oxford University Press, 1997. http://dx.doi.org/10.1093/oso/9780195098235.003.0014.
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Small molecules consisting of light-, few-electron atoms were the first species beyond atoms to yield to quantum-mechanical methods. Similarly, crystals of small light-atom molecules have served as most useful test cases of charge density mapping. The small number of core electrons in first-row atoms enhances the relative contribution of valence electron scattering to the diffraction pattern. Early studies, done just after automated diffractometers became widely available, were concerned with molecular crystals such as uracil (Stewart and Jensen 1967), s-triazine (Coppens 1967), oxalic acid dihydrate (Coppens et al. 1969), decaborane (Dietrich and Scheringer 1978), fumaramic acid (Hirshfeld 1971), glycine (Almlof et al. 1973), and tetraphenylbutatriene (Berkovitch-Yellin and Leiserowitz 1976). While thermal motion is often pronounced in molecular crystals, advances in low-temperature data collection have done much to alleviate this disadvantage. In recent years, subliquid-nitrogen cooling techniques have been increasingly applied. Among the most interesting aspects of molecular crystals are the influence of intermolecular interactions on the electronic structure. Physically meaningful Coulombic parameters pertinent to a molecule in a condensed environment can be obtained from the diffraction analysis, and can be used in the modeling of macromolecules. The enhancement of the electrostatic moments relative to those of the isolated species has been noted in chapter 7. But, beyond these considerations, molecular crystals are important in their own right. For example, crystals of aromatic molecules substituted with π-electron donor and acceptor groups are among the most strongly nonlinear optical solids known, considerably exceeding the nonlinearity of inorganic crystals such as potassium titanyl phosphate (KTP); while mixed-valence organic components of low-dimensional solids can become superconducting at low temperatures. The relation between such properties of molecular crystals and their charge distribution provides a continuing impetus for further study. The suitability of light-atom crystals for charge density analysis can be understood in terms of the relative importance of core electron scattering. As the perturbation of the core electrons by the chemical environment is beyond the reach of practically all experimental studies, the frozen-core approximation is routinely used. It assumes the intensity of the core electron scattering to be invariable, while the valence scattering is affected by the chemical environment, as discussed in chapter 3.