Tài liệu miễn phí Hoá học
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Ring opening and ring closure reactions of chromone-3-carboxylic acid: unexpected routes to synthesize functionalized benzoxocinones and heteroannulated pyranochromenes
Unexpected routes to synthesize functionalized benzoxocinones and heteroannulated pyranochromenes were achieved via transformations of the γ -pyrone ring in chromone-3-carboxylic acid throughout its reactions with some acyclic and cyclic carbon nucleophiles. A key part of the reaction mechanisms is discussed. Structures of the new synthesized products were established on the basis of elemental analysis and spectral data (IR, MS, and 1H and 13C NMR).
4/5/2023 5:21:52 AM +00:00
Gaseous and dissolved oxygen sensing with stabilized pyrene in ionic liquid modified electrospun slides
Pyrene dye has many superior characteristics for oxygen sensing studies such as long fluorescence lifetime, high quantum yield, and good sensitivity. It is preferred in some cases over ruthenium dyes for its more lipophilic character and higher sensitivity. However, easy photodegradation of pyrene is a challenging problem. In this study, pyrene dye was for the first time immobilized in an ethyl cellulose matrix and used for oxygen sensing in the form of thin films and electrospun sensing slides.
4/5/2023 5:21:45 AM +00:00
Redox polymerization of N-isopropylacrylamide by using hydroxylated soya oil polymer
Water soluble hydroxylated soya oil polymer was used in the redox polymerization of N-isopropylacrylamide (NIPAM) in order to obtain water-based hydroxylated-soya oil polymer-g-PNIPAM graft copolymer. For this purpose, soya oil was exposed to air under sunlight to obtain autoxidized soya oil polymer (PSy-ox). PSy-ox was allowed to react with diethanol amine to obtain hydroxylated soya oil polymer (hydroxylated-PSy). An ammonium persulfate with hydroxylated-PSy redox initiating system was used in the polymerization of NIPAM in order to obtain thermoresponsive hydroxylated-PSy-g-PNIPAM water-based graft copolymers.
4/5/2023 5:21:38 AM +00:00
HPLC fluorescence determination of ochratoxin A utilizing a double internal standard and its application to poultry feed
A validated liquid chromatography method employing a fluorescence detector for the determination of ochratoxin A (OTA) was developed with double internal standard and it was applied to ten different poultry feeds. The analysis was performed in an octadecyl silane column using a solvent system [ACN:water:formic acid (50:50:1.25, v/v/v)] by isocratic elution. The flow rate and injection volume were 1 mL min−1 and 12 µL, respectively.
4/5/2023 5:21:31 AM +00:00
Selective CO methanation over NiO–Al2O3–ZrO2 and Co3O4–Al2O3–ZrO2 catalysts
NiO–Al2O3–ZrO2 and Co3O4–Al2O3–ZrO2 catalysts were prepared by three different co-precipitation methods, namely co-precipitation, surfactant-assisted co-precipitation, and surfactant-assisted co-precipitation with ultrasound mixing methods, and their activities were tested in selective CO methanation. Catalysts were characterized using N2 physisorption, XRD, SEM, TEM, XPS, and TPR-H2 techniques. CO methanation and selective CO methanation reactions were carried out. Catalysts prepared by surfactant assisted co-precipitation gave high surface area, uniform pore size distributions, and small pores.
4/5/2023 5:21:21 AM +00:00
Synthesis and electrochemistry of phthalocyanines bearing [(3,4-dimethoxybenzyl)oxy] groups
In this study peripherally tetra-substituted metal-free, metallophthalocyanines bearing (3,4-dimethoxybenzyl) oxy groups have been synthesized and characterized. Electrochemical properties of novel phthalocyanines 4, 5, 6, and 7 were determined by cyclic and square wave voltammetry in order to define their possible applications in different electrochemical technologies. CoII and TiIVO metal ions behave as redox active cations in the core of the CoPc and TiOPc complexes, respectively
4/5/2023 5:21:14 AM +00:00
Synthesis and biological evaluation of new pyridines containing imidazole moiety as antimicrobial and anticancer agents
The synthesis of a novel series of pyridine and bipyridine derivatives is described via one-pot multicomponent reaction of 5-acetylimidazole, malonitrile (or ethylcyanoacetate or diethylmalonate), substituted benzaldehyde (or terephthaldehyde), and ammonium acetate in good yields. The structures of all the new compounds were elucidated on the basis of elemental analysis and spectral data. The antimicrobial activities of the synthesized compounds were screened and the results showed that most of such compounds exhibit considerable activities.
4/5/2023 5:21:07 AM +00:00
Improvement of solubility of celecoxib by inclusion in MCM-41 mesoporous silica: drug loading and release
Celecoxib is a poorly water-soluble nonsteroidal anti-inflammatory drug. Here we report four ordered mesoporous silica MCM-41 supports with different particle size, pore volume, and surface properties to investigate their loading capacity with celecoxib and their release abilities. Spherical MCM-41 mesoporous supports less than 50 nm in diameter were prepared and to compare the effect of the template removal process on morphology of samples, acid extraction and calcination methods were used. Moreover, nearly 500 nm sized rod-shaped MCM-41 mesoporous silica was obtained by changing the template concentration in preparation.
4/5/2023 5:20:52 AM +00:00
Molecular docking analysis and molecular dynamics simulation study of ameltolide analogous as a sodium channel blocker
Fifteen compounds related to ameltolide with sodium channel inhibitory activity were subjected to a molecular docking study. The chemical structures of all compounds were built using the program HyperChem and conformational studies were performed with a semiempirical method followed by the PM3 method. A docking study was performed using the program AutoDock on all the compounds. To confirm the binding mode of inhibitors, molecular dynamics simulations were performed using GROMACS 4.5.5, based upon the docked conformation of ameltolide.
4/5/2023 5:20:44 AM +00:00
Effect of sonic treatment on the permeation performance of cellulose acetate membranes modified by n-SiO2
Cellulose acetate (CA) membranes were modified by nano-silicon dioxide (n-SiO2), and they were exposed to ultrasonic waves at a frequency of 35 kHz. The effect of sonication on their water sorption tendency and permeation capability was investigated. The characterization of the membranes was done by FTIR and SEM analysis, and the hydrophilic character of the membranes was deduced by swelling studies and contact angle (CAn) measurements.
4/5/2023 5:20:37 AM +00:00
PFAM catalyzed enantioselective diethylzinc addition to imines
Chiral amines are important starting materials for the synthesis of biologically important compounds. Enantioselective addition of dialkylzinc reagents to imines is a reliable method for the synthesis of these compounds. Different chiral catalysts were developed and used for this method. Phosphorous based PFAM catalysts were tried for the first time in the enantioselective synthesis of amines by reacting diethylzinc with N-sulfonyl imines and Ndiphenylphosphinoyl imines. Chiral amines were isolated with moderate to acceptable yields and enantioselectivities.
4/5/2023 5:20:31 AM +00:00
The synthesis of 1,3-dialkyl-4-methylimidazolinium salts and their application in palladium catalyzed Heck coupling reactions
Seven novel 1,3-dialkyl-4-methylimidazolinium chloride salts 3a–g were prepared as precursors of N-heterocyclic carbenes by reacting N,N’-alkyl-1,2-diaminopropane, triethyl orthoformate, and ammonium chloride. The salts were characterized spectroscopically. The in situ prepared palladium complexes derived from the imidazolinium salts and palladium acetate were used as catalyst in Heck coupling reactions between aryl bromides and styrene. The corresponding Heck products were obtained in good yields.
4/5/2023 5:20:24 AM +00:00
Synthesis, structural characterization, and antimicrobial efficiency of sulfadiazine azo-azomethine dyes and their bi-homonuclear uranyl complexes for chemotherapeutic use
The analytical and spectral data supported the binuclear formulation of the complexes with a 2:1 metal to ligand ratio and octahedral geometry. The molar conductance values of the UO2 (II)-complexes revealed their nonionic character. The ligands and their complexes were screened for their antibacterial activities towards the gram-positive Staphylococcus aureus and the gram-negative Escherichia coli, as well as their antifungal activities against Aspergillus niger and Candida albicans, in order to assess their antimicrobial potential. The results showed that metallization increases antimicrobial activity compared with the free ligands.
4/5/2023 5:20:17 AM +00:00
Revisiting the biodesulfurization capability of hyperthermophilic archaeon Sulfolobus solfataricus P2 revealed DBT consumption by the organism in an oil/water two-phase liquid system at high temperatures
The ability of the hyperthermophilic archaeon Sulfolobus solfataricus P2 to grow on organic and inorganic sulfur sources was investigated. A sulfur-free mineral medium was employed with different sources of carbon. The results showed that inorganic sulfur sources display growth curve patterns significantly different from the curves obtained with organic sulfur sources. Combustion of fossil fuels leads to the atmospheric emission of sulfur oxides that contribute to acid rain and air pollution.
4/5/2023 5:20:11 AM +00:00
Regiospecific one-pot, combinatorial synthesis of new substituted pyrimido[4,5-c]pyridazines as potential monoamine oxidase inhibitors
New 3-aryl-6-methylpyrimido[4,5-c]pyridazine-5,7(6H,8H)-diones and 3-aryl-6-ethyl-7-thioxo-7,8-dihydropyrimido[4,5-c]pyridazin-5(6H)-ones were efficiently synthesized via a regiospecific one-pot reaction of N-methylbarbituric acid and N -ethyl-2-thiobarbituric acid with various arylglyoxal monohydrates in the presence of hydrazine dihydrochloride in ethanol at 50◦C. The target compounds were obtained in high yields and were regioisomerically pure after recrystallization. These new heterocycles may act as potential MAO B inhibitors.
4/5/2023 5:20:04 AM +00:00
Synthesis of new oxindole derivatives containing benzothiazole and thiazolidinone moieties using nano silica-bonded 5-n-propyl-octahydro-pyrimido[1,2-a]azepinium chloride (NSB-DBU) as catalyst
A facile one-pot synthesis of novel oxindole derivatives bearing benzothiazolylmethyl-2-thioxothiazolidin-4- one was accomplished via one-pot reaction of 5-oxoindolinylidene rhodanine-3-acetic acid derivatives, 2-aminothiophenol, and triphenyl phosphite in the presence of tetrabutylammonium bromide (TBAB) and nano silica-bonded 5-n-propyloctahydro-pyrimido[1,2-a]azepinium chloride (NSB-DBU) as heterogeneous reusable nanocatalyst. The target compounds were obtained in excellent yields (85%–92%) and short reaction times under fairly mild reaction conditions.
4/5/2023 5:19:57 AM +00:00
A green light emitting polymer in a PMMA matrix: oligo(azomethine-ether) with benzothiazole moieties
This study aimed to synthesize an oligo(azomethine-ether) with benzothiazole moiety in organic medium by means of chemical oxidative polycondensation (OP). Optical properties were examined by photoluminescence (PL) and UV-Vis measurements both in solutions and solid film involved a poly (methyl methacrylate) (PMMA) matrix. Oligomer film in the PMMA matrix emitted a fine green light with a fluorescence quantum yield (QY) of 3.30%. Spectral and thermal observations showed a high rate of C–O–C coupling (cross-linking) for the oligomer.
4/5/2023 5:19:50 AM +00:00
Fluorescent mono- and tetra-dansylated cavitands: synthesis and acid sensitivity
Two fluorescent tetra- and mono-dansylated resorcinarene cavitands were prepared and fully characterized. The X-ray structure of mono-dansylated resorcinarene cavitand was obtained. Their intrinsic absorption and fluorescence properties were studied. These properties were strongly sensitive to the presence of perchloric acid, as evidenced by the appearance of isobestic points upon protonation of the dansyl dimethylamino functions. The decreasing of the fluorescence emission intensity upon titration with perchloric acid was explained by the excited state interactions between the dansyl groups of the resorcinarene.
4/5/2023 5:19:43 AM +00:00
Synthesis of methyl 4-(9H-carbazole-9-carbanothioylthio) benzoate: electropolymerization and impedimetric study
Methyl 4-((9H-(carbazole-9-carbanothioylthio) benzoate (MCzCTB) was chemically synthesized and characterized by FTIR, 1H NMR, and 13C NMR. A novel synthesized monomer was electropolymerized on a glassy carbon electrode (GCE) in various initial molar concentrations of [MCzCTB] 0 = 1,3,5, and 10mM in 0.1M NaClO4/CH3CN and 1M H2SO4. P(MCzCTB)/GCE was characterized by cyclic voltammetry, Fourier transform infrared-attenuated transmittance reflectance, scanning electron microscopy-energy dispersive X-ray, and electrochemical impedance spectroscopy.
4/5/2023 5:19:35 AM +00:00
Synthesis, molecular docking, and antitumoral activity of alnustone-like compounds against estrogen receptor alpha-positive human breast cancer
Alnustone-like compounds are promising inhibitors for estrogen receptor α (ER-α), which is a novel cancer therapeutic target. Therefore, 10 alnustone-like compounds with substituents at the phenyl rings were synthesized by condensation of 4-phenyl-2-butanones and cinnamaldehydes via in situ enamination. The compounds displayed either protective activity or inhibited cell growth and proliferation of human breast cancer cells. Molecular docking studies indicated that the synthesized compounds interact with ER-α efficiently.
4/5/2023 5:19:28 AM +00:00
Deposition of cadmium sulfide and zinc sulfide thin films by aerosol-assisted chemical vapors from molecular precursors
The as-deposited thin films were characterized by powdered X-ray diffraction and field emission scanning electron microscopy. Thin films of CdS deposited at low temperature (350◦C) consist of densely packed granular crystallites with an average size of ca. 150 nm, while at higher temperatures (400 and 450◦C) particles with varying sizes and mixed morphologies are observed. The ZnS thin films deposited at 400◦C showed rod-like structures, whereas dense globular-like structures were obtained at 450◦C. Energy dispersive X-ray analysis was performed to study the chemical composition of the thin films.
4/5/2023 5:19:21 AM +00:00
Preparation of visible light sensitive nano-sized N-TiO2 photocatalysts and their photocatalytic activity under visible light
This study aimed to develop a photocatalyst that responds to visible light. For the preparation of visible light sensitive photocatalysts, N was doped into TiO2(N-TiO2). To inhibit the recombination of excited electrons and holes, transition metals (M = Pt, Cu, Fe, Cr) were loaded on the N-TiO2. N-TiO2 nanotubes were also synthesized by a hydrothermal treatment of the prepared N-TiO2 in a strong basic environment. The prepared photocatalysts were characterized by XRD, FESEM, HRTEM, XPS, and UV/VIS spectrophotometer, and their photocatalytic activity was tested by the photodecomposition of liquid-phase methylene blue and gas-phase acetone.
4/5/2023 5:19:13 AM +00:00
Purification and characterization of NADPH-cytochrome P450 reductase from Lake Van fish liver microsomes and investigation of some chemical and metals’ effects on the enzyme activity
In addition, optimum ionic strength, optimum pH, optimum temperature, and stable pH values were determined for the enzyme in the kinetic studies performed. K M and Vmax were determined for NADPH and cytochrome c. Effects of some metals ions, antibiotics, and some other drugs used in aquarium fisheries on the activity of the enzyme were investigated. IC50 values and Ki values of metals showing an inhibitory effect were calculated.
4/5/2023 5:19:07 AM +00:00
Synthesis, properties, and electrochemistry of a photochromic compound based on dithienylethene and ProDOT
The synthesis, photochromic features, and electrochemistry of a novel material based on dithienylethene (DTE) and 3,3-didecyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepine (didecyl-ProDOT) units are described. It is noteworthy that 1,2-bis(5-(3,3-didecyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepin-6-yl)-2-methylthiophen-3-yl)cyclopent-1-ene can be efficiently switched between open and closed states by light in both solution and in the solid poly(methyl metacrylate) (PMMA) matrix. It is also found that the emission of this novel compound can be switched on and off upon irradiation.
4/5/2023 5:18:59 AM +00:00
Synthesis and properties of novel magnetic nanoparticles grafted with nitropyridine-substituted calix[4]arene derivative as Cr6+ extractant
The structure of the calixarene-adorned magnetic nanoparticles 4 was determined by a combination of FTIR, TEM, and elemental analysis. Moreover, a study regarding the removal of toxic HCr2O−7 anion from aqueous solution was also carried out with the calixarene-adorned magnetic nanoparticles in solid–liquid extraction studies.
4/5/2023 5:18:53 AM +00:00
Synthesis of tetrahydropyrimidinium salts and their in situ catalytic activities towards the Buchwald–Hartwig amination reaction under microwave irradiation
A series of asymmetrical substituted tetrahydropyrimidinium salts and different kinds of bridged bistetrahydropyrimidinium salts were prepared through the quaterization of tetrahydropyrimidine or the dehydrogenation of hexahydropyrimidine. They were characterized and used as NHC precursors in the palladium catalyzed Buchwald– Hartwig amination reaction. The in situ formed catalytic system Pd(OAc)2/tetrahydropyrimidinium and t BuOK catalyzed the amination of heteroaryl halides and heterocyclic amines effectively, producing the heterocyclic amine functionalized heteroaryl derivatives in high yields.
4/5/2023 5:18:47 AM +00:00
Synthesis and characterization of substituted benzimidazole Co(II), Fe(II), and Zn(II) complexes and structural characterization of dichlorobis{1-[2-(1-piperidinyl)ethyl]-1H-benzimidazole-K N3} zinc(II)†
The Co(II), Fe(II), and Zn(II) complexes of 1-(3-phenyl)propylbenzimidazole (PPBI), 5-nitro-1-(3-phenyl) propylbenzimidazole (PPNBI), 1-[2-(4-morpholinyl)ethyl]benzimidazole (MEBI), 1-[2-(1-piperidinyl)ethyl]benzimidazole (PEBI), and 5-nitro-1-[2-(1-piperidinyl)ethyl]benzimidazole (PENBI) were synthesized and characterized by 1H NMR, 13C NMR, and elemental analyses. The magnitudes of the magnetic moments for paramagnetic complexes were between 4.07 and 5.11 B.M. Moreover, the crystal structure of dichlorobis{1-[2-(1-piperidinyl)ethyl]-1H-benzimidazole-KN3} zinc(II) was determined by single crystal X-ray diffraction.
4/5/2023 5:18:40 AM +00:00
Effect of acrylic acid feed contents of microgels on catalytic activity of silver nanoparticles fabricated hybrid microgels
This decrease in induction time was due to decrease in the surface area of nanoparticles present within the microgels with an increase in the feed contents of acrylic acid. The decrease in the value of apparent rate constant was due to an increase in the size of nanoparticles fabricated within the microgels with an increase in mol percentage of acrylic acid. The linear relation between apparent rate constant and feed contents of acrylic acid can be used for quantitative analysis of contents of acrylic acid present in polymer microgels.
4/5/2023 5:18:32 AM +00:00
Amperometric biosensing of ethanol based on integration of alcohol dehydrogenase with a Pt/PPy–PVS/MB electrode
The results showed that 95.7% of the response current was retained after 17 activity assays. The ethanol biosensor gave perfect reproducible finding with 4.6% relative standard deviation. The prepared biosensor retained 55.8% of initial activity after 24 days when stored in 0.1 M phosphate buffer solution at 4 ◦ C. Effects of the several possible interfering substances such as ascorbic acid, citric acid, and methanol on the ethanol biosensor were investigated and the developed biosensor was tested in alcoholic beverages.
4/5/2023 5:18:23 AM +00:00
Synthesis and molecular modeling studies of naproxen-based acyl hydrazone derivatives
A series of N-acylhydrazone derivatives (2a–2p) containing 6-methoxy-naphthalene and acylhydrazone moieties were synthesized in good yield using microwave irradiation and developed as potential COX-2 inhibitors. Furthermore, the interactions between COX-2 and the compounds were examined in detail by molecular modeling studies such as structure–activity relationship and molecular docking performed using Gaussian 09 and Discovery Studio 3.5. As a result, it was found that N-acylhydrazone compounds displayed a different mechanism than SC-558 as COX-2 inhibitor by binding to different active sites of the protein, COX-2. Compound 2c would be a good COX-2 inhibitor candidate for preclinical studies.
4/5/2023 5:18:15 AM +00:00