Crown Ether
Mostrando 1-12 de 12 artigos, teses e dissertações.
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1. Elemental Chalcogen (Se, S) in PEG-400 to the Synthesis of Seleno- and Thioflavones from 2-Chlorophenyl Ethynyl Ketone and Nucleophilic Species of Chalcogen
An alternative green method was developed for the synthesis of thio-and selenoflavones by the ring closure of 2-chlorophenyl ethynyl ketone with NaHY (Y = S, Se). These nucleophilic chalcogen species were generated in situ using NaBH4 to reduce the elemental chalcogen in the presence of polyethylene glycol-400 (PEG-400). The efficiency of this reaction is st
J. Braz. Chem. Soc.. Publicado em: 2021-08
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2. Fast Triacylglycerol Screening and Semi-Quantitative Analysis of Fatty Acids in Commercial Oils by DIMS with 18-Crown-6 Ether/Trifluoracetic Acid Dopants
Vegetable oil analyses, especially due to the complexity of the oil components, are commonly laborious, requiring several analytical techniques. In this work, electrospray ionization mass spectrometry with direct injection (DIMS), along with 18-crown-6 ether (crown ether) chelating agent and trifluoroacetic acid (TFA), was used to characterize and semi-quant
J. Braz. Chem. Soc.. Publicado em: 2019-02
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3. Eletrodo íon-seletivo de pasta de carbono para determinação de cobre baseado em um novo Lariat-éter coroa.
Sensores potenciométricos são conhecidos por sua alta sensibilidade e seletividade. Tais sensores apresentam versatilidade, baixo custo e robustez, o que garante a esses sensores aplicabilidade em uma grande variedade de amostras químicas complexas. Os eletrodos íon-seletivos de membrana polimérica são os sensores potenciométricos mais conhecidos, por
IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia. Publicado em: 201103
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4. Ãteres coroa com Ãons lantanÃdeos: de compostos de coordenaÃÃo a novos materiais nanoestruturados de sÃlica
Com o objetivo de desenvolver novos materiais e ligantes, baseados em Ãteres coroa, capazes de coordenarem um ou mais Ãons lantanÃdeos, o presente trabalho mostra a sÃntese de compostos de coordenaÃÃo mono e binucleares, livres ou ligados Ãs matrizes de sÃlica. As caracterizaÃÃes foram realizadas via anÃlise elementar, anÃlise termogravimÃtrica,
Publicado em: 2008
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5. Modelagem e sÃntese de Ãteres-coroa contendo o grupo sulfÃxido e seus complexos com Ãons lantanÃdeos
As sÃnteses de novos Ãteres-coroa, com grupos sulfÃxido, foram testadas visando suas aplicaÃÃes como ligantes em compostos de coordenaÃÃo com Ãons lantanÃdeos. As estruturas dos Ãteres-coroa e de seus complexos com o Eu3+ foram obtidas com o mÃtodo SMLC/AM1. Os resultados para a complexaÃÃo foram favorÃveis para os seguintes compostos: 2,3,11,1
Publicado em: 2006
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6. New class of crowned porphyrins: analytical application and catalytic activity in the oxidation of hydrocarbons and carbamazepine drug. / Nova classe de porfirinas substituídas com éter coroa: Aplicação analítica e atividade catalítica na oxidação de hidrocarbonetos e do fármaco carbamazepina
Neste trabalho foi realizada a síntese, purificação e caracterização de uma tetra crowned porfirina, a 5,10,15,20-tetraquis[2-(hexaoxacicloexadecano-3-amidafenil)]-porfirina, H2TCP, bem como a correspondente ferroporfirina, (FeTCP)Cl. Foi investigado a atividade catalítica desta ferroporfirina e da ferroporfirina mono-crowned substituída, (FeMCP)Cl, s
Publicado em: 2006
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7. Estudo fisico-quimico do transporte de especies quimicas atraves de membranas liquidas hidrofobicas em tempo real
Transport processes of variated chemical species - potassium ions, amino acids and vitamins - through hidrophobic liquid membranes was studied using BLM (bulk liquid membrane) method. UV - Vis spectroscopy was used in all cases to quantify the tranported species. It was not possible to use univariate calibration in cases of simultaneous transport because the
Publicado em: 2000
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8. Transfer activity coefficients between water and methanol of complexes of some univalent and barium ions with dibenzocryptand 2.2.2, cryptand 2.2.2, and 18-crown-6
Stability constants, KfLMn+ (in which L = ligand and Mn+ = metal ion), of complexes of sodium, potassium, silver, thallium(I), and barium with dibenzocryptand 2.2.2 were determined at 25°C in water and methanol. Also determined were transfer activity coefficients between methanol and water of two ligands, dibenzocryptand 2.2.2 and 18-crown-6. From these dat
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9. Singlet molecular oxygen in the Haber-Weiss reaction.
Characteristic chemiluminescence emission of singlet (1 delta g) molecular oxygen at 1268 nm is reported from a Haber-Weiss reaction. The reaction consists of mixing aqueous hydrogen peroxide with a solution of potassium superoxide, solubilized by 18-crown-6 ether in carbon tetrachloride or in dry acetonitrile at room temperature. Since the discovery of the
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10. Liquid chromatographic determination of amoxicillin concentrations in bovine plasma by using a tandem solid-phase extraction method.
We report a means of determining amoxicillin in bovine plasma by liquid chromatography with UV detection at 235 nm. Purification and concentration of extracts were accomplished by a tandem solid-phase extraction procedure with two reversed-phase columns. Separation of amoxicillin from interferences was improved by the incorporation of a crown ether in the so
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11. Liquid chromatographic determination of ampicillin in bovine and dog plasma by using a tandem solid-phase extraction method.
The determination of ampicillin in plasma and serum by reversed-phase high-performance liquid chromatography with UV detection suffers from poor selectivity and sensitivity. Currently, the most common approach to overcoming these problems consists of improving the compound's detectability via pre- or postcolumn derivatization. In the method that we describe,
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12. A Ba2+ chelator suppresses long shut events in fully activated high-conductance Ca(2+)-dependent K+ channels.
High-conductance Ca(2+)-activated K+ channels from rat skeletal muscle were incorporated into planar lipid bilayers, and the channel kinetics were studied with a high internal Ca2+ concentration (Cai). Raising the Cai is known to increase the channel open probability. This effect is due to an increases in openings frequency and duration, and saturates at a C