Tài liệu miễn phí Hoá học
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Comparative study of microwave-assisted and conventional synthesis of ibuprofen-based acyl hydrazone derivatives
A series of potential biological active acyl hydrazone derivatives containing ibuprofen moiety (compounds 4a–4p) was synthesized by the condensation of ibuprofen hydrazone with aromatic aldehydes using conventional and microwave irradiation methods. The microwave method was found to be successful with nearly the same or higher yields and shorter reaction time, and it was more environmentally friendly compared to the conventional heating method. The chemical structures of the synthesized compounds were characterized by IR, 1H NMR, and APT-NMR spectroscopy.
4/5/2023 5:01:21 AM +00:00
Sesquiterpene hydrocarbons of the essential oil of Actinolema macrolema Boiss
The essential oils of Actinolema macrolema Boiss. (Apiaceae) were obtained by hydrodistillation in the first 3 (sample A) and the following 3 h (sample B) from crushed fruits and dried leaves (sample C), which were subsequently analyzed by GC and GC-MS. Overall, 64 components were characterized, representing 93% of the leaf oil. Thirty components were characterized from the fruit oil representing 95% of the first fraction and 90% of the second fraction consecutively. Guaia-5,7(11)-diene, selina-3,7(11)-diene, and juniper camphor were isolated from the oils by column chromatography and their structures were elucidated by GC-MS, 1H NMR, and 13C NMR.
4/5/2023 5:01:13 AM +00:00
Synthesis of new N-[3-(Benzo[d]thiazol-2-yl)-4-methylthiazol-2(3H)-ylidene] substituted benzamides
A series of novel N -[3-(2-benzo[d]thiazol-2-yl)-4-methylthiazol-2(3H)-ylidene] substituted benzamides (2a–k) were efficiently synthesized by heterocyclization of the corresponding 1-(benzo[d]thiazol-2-yl)-3-aroylthioureas (1a–k). The cyclization was achieved by the reaction of α-bromoacteone produced in situ using bromine in dry acetone in the presence of triethylamine.
4/5/2023 5:01:07 AM +00:00
Simple and convenient preparation of novel 6,8-disubstituted quinoline derivatives and their promising anticancer activities
A short and easy route is described for 6,8-disubstituted derivatives of quinoline and 1,2,3,4-tetrahydroquinoline from 6,8-dibromoquinolines 2 and 7 by various substitution reactions. While copper-promoted substitution of 6,8- dibromide 2 produced monomethoxides 3 and 4, a prolonged reaction time mainly afforded dimethoxide 6 instead of 5, whose aromatization with DDQ and substitution reaction of dibromide 7 with NaOMe in the presence of CuI also gave rise to dimethoxide 6. Several 6,8-disubstituted quinolines were obtained by treatment of 6,8-dibromoquinoline (7) with n-BuLi followed by trapping with an electrophile [Si(Me)3Cl, S2(Me)2, and DMF].
4/5/2023 5:01:00 AM +00:00
Synthesis, characterization, and fluorescence study of phthalhydrazidylazo derivative of an unsaturated diketone and its metal complexes
The Ni(II) and Zn(II) chelates are diamagnetic while Cu(II) complex showed normal paramagnetic moment. The fluorescence maxima of the compound in different solvents show that the emission wavelength increases with increases in the polarity of the solvent. The fluorescence intensity in the presence of Cu(II) ion shows a gradual decrease with increases in the concentration of metal ion.
4/5/2023 5:00:53 AM +00:00
Synthesis of tetrakis(carboxyphenyl)porphyrin coated paramagnetic iron oxide nanoparticles via amino acid for photodegradation of methylene blue
In this paper, synthesis of tetrakis(carboxyphenyl)porphyrin (TCPP) coated cadmium ferrite (CdFe 2 O4) nanoparticles by using L-lysine as an anchor is reported for the first time. The ferrimagnetic CdFe 2 O4 nanoparticles were prepared via the facile self-assembly method of reflux followed by a heating treatment. The obtained magnetic nanoparticles were coated with TCPP in the presence of the amino acid L-lysine by sonication in ethanol and then refluxing for 12 h. The structural characteristics of the products were determined using FT-IR and XRD pattern. Scanning electron microscopy (SEM) images indicated uniform morphologies of the magnetic nanoparticles with an average size of 43 nm.
4/5/2023 5:00:21 AM +00:00
Synthesis, characterization, and DFT calculation of a Pd(II) Schiff base complex
Comparison between the calculated and experimental results covering molecular structures, assignment of fundamental vibrational modes, and thermodynamic properties were investigated. The optimized molecular geometries were compared with the experimental data obtained from X-ray data of a similar complex, which indicated that the theoretical results agree with the corresponding experimental values. The UV-Vis spectrum of the compound was also recorded and some properties, such as HOMO and LUMO energies and λmax , were determined using DFT (PW91) method. The absorption wavelengths were compared with the experimental data.
4/5/2023 5:00:05 AM +00:00
Biodegradability of degradable mulching film in a laboratory-controlled composting test
A series of degradable films was prepared, and 2 formulas of polyethylene (PE) films with the highest degradable performance were experimentally determined. These films contained 3.43% and 0.44% stearate, and were denoted as PE-3 and PE-4, respectively. Their biodegradability was studied in a laboratory-controlled composting test using ordinary PE film (OPEF) as a control. Contrast composting experiments indicated that the biodegradability of untreated samples was very low, and that the biodegradation rates of PE films after natural aging were significantly higher.
4/5/2023 4:59:57 AM +00:00
Synthesis of 3,4-diaryl-1-phenyl-4,5-dihydro-1H -pyrazole-5-carbonitriles via 1,3-dipolar cycloaddition reactions
Nitrile imines generated by the oxidative dehydrogenation of aromatic aldehyde phenylhydrazones with chloramine-T as a catalytic dehydrogenating agent were trapped in situ by 4-methoxy cinnamonitrile to afford 3,4- diaryl-1-phenyl-4,5-dihydro-1H -pyrazole-5-carbonitrile in moderate to good yields. The structures of the cycloadducts were confirmed by spectral studies and elemental analysis.
4/5/2023 4:59:51 AM +00:00
Molecular mechanism of Diels–Alder reaction between (E)-3,3,3-trichloro-1-nitropropene and cyclopentadiene: B3LYP/6-31G(d) computational study
Analysis of reactivity indexes supports the polar character of the reaction between (E)-3,3,3-trichloro-1- nitropropene and cyclopentadiene. This is confirmed by the analysis of electronic properties of transition complexes involved in the reaction paths using the B3LYP/6-31G(d) algorithm. The transition state’s asymmetry is large, but it is insufficient to provoke a zwitterionic reaction mechanism. Attempts to find a heterocyclic intermediate 7 in the reaction path ultimately leading to 5-endo-nitro-6-exo-trichloromethylnorbornene 3 have been unsuccessful.
4/5/2023 4:59:41 AM +00:00
Palladium-EDTA and palladium-EdteH4 catalyzed Heck coupling reactions in pure water
Palladium-catalyzed Heck coupling reactions of styrene with bromoarene derivatives are carried out under aerobic conditions in water using water-soluble N,N,N′,N′-tetrakis(2-hydroxyethyl)ethylenediamine (EdteH4) and ethylenediaminetetraacetic acid disodium salt (Na2EDTA) as ligands. The effect of different bases, catalyst loading, and additives is also monitored.
4/5/2023 4:59:35 AM +00:00
A new anthracene derivative of calix[4]arene as a fluorescent chemosensor
A new anthracene derivative of calix[4]arene was synthesized as a highly fluorescent compound. This compound was examined for its fluorescent properties towards different metal ions (Li+, Na+, Mg2+, Ca2+, Ba2+, Ni2+, Cu2+, Zn2+, Pb2+) by UV and fluorescence spectroscopy. On complexation by alkaline earth metal cations and transition metal cations, the fluorescence spectrum was quenched. In particular, Ca2+ caused greater than 98% quenching of the anthracene derivative of calix[4]arene.
4/5/2023 4:59:23 AM +00:00
A kinetic study of atom transfer radical polymerization of styrene with bis(2-pyridyl)ethylenedimethanimine derivative ligands
Atom transfer radical polymerization (ATRP) of styrene was carried out with multidentate nitrogenbased ligands, namely N,N’-bis[phenyl(pyrid-2-yl)methylene] ethane-1,2-diamine (BPDA) and N,N’-bis[methyl(pyrid2-yl)methylene] ethane-1,2-diamine (BMDA), and catalyst systems at catalyst/ligand molar ratios of 1/0.33, 1/0.5, 1/1, and 1/1.5 by using 2 different initiators, (1-bromoethyl)benzene (BEB) and ethyl-2-bromopropionate (EBP). Linear first-order kinetic plots were observed for ATRP of styrene upon using BPDA as a ligand with both initiators.
4/5/2023 4:59:13 AM +00:00
Synthesis and biological activities of methylenebis-4H -1,2,4-triazole derivatives
The newly synthesized compounds were screened for their antimicrobial activities; some of them were found to be active towards the test microorganisms as the results demonstrated that the synthesized compounds exhibited a broad spectrum of activity with minimum inhibitory concentration (MIC) values of 31.3–500 µg/mL against gram-positive and gram-negative bacteria, Candia albicans and Saccharomyces cerevisiae.
4/5/2023 4:59:07 AM +00:00
Determination and evaluation of gross alpha and beta activity concentrations and metal levels in thermal waters from Ankara, Turkey
The gross α and β activity concentrations in the thermal waters of Karakaya-Aya¸s, ˙I¸cmece-Aya¸s, Beypazarı (Dutluk-Tahtalı), Haymana, and Kızılcahamam spas in Ankara Province were measured by MPC-9604 multi-detector α/β counting system. Ranges of activity concentrations found were from 0.09 to 2.58 Bq L−1 for gross α and from 0.25 to 2.61 Bq L−1 for gross β. The ranges of minimum detectable concentrations for gross α (0.05–0.41 Bq L−1 ) and for gross β (0.04–0.29 Bq L−1 ) were obtained.
4/5/2023 4:59:00 AM +00:00
Aerosol-assisted chemical vapor deposition of copper sulfide nanostructured thin film from newly synthesized single-source precursor
The copper(II) complex of N -[ethyl(butyl)carbamothioyl]-3,5-dinitrobenzamide (1) has been synthesized and characterized by elemental analysis, IR spectroscopy, and atmospheric pressure chemical ionization-mass spectrometry. Thermogravimetric analysis shows that complex 2 decomposes in 2 steps to form copper sulfide. The complex was used as a single-source precursor for the deposition of copper sulfide thin film by aerosol-assisted chemical vapor deposition at 350◦C.
4/5/2023 4:58:13 AM +00:00
Synthesis, spectroscopic characterization, and biological screening of binuclear transition metal complexes of bicompartmental Schiff bases containing indole and resorcinol moieties
A series of binucleating Cu(II), Ni(II), and Zn(II) complexes of bicompartmental ligands with ONO donors were prepared. The ligands were synthesized by the condensation of 5-substituted-3-phenyl-1H -indole-2-carboxyhydrazides and 4,6-diacetylresorcinol. The newly synthesized ligands and their complexes were characterized by elemental analysis and various spectral studies like IR, 1H NMR, ESI-mass, UV-Vis, ESR, thermal studies, magnetic susceptibility, molar conductance, and powder-XRD data.
4/5/2023 4:58:02 AM +00:00
Optimization of synthesizing glucose 1-phosphate by sodium tripolyphosphate as a phosphorus acylating agent using response surface methodology
With glucose as the starting material, sodium tripolyphosphate as the phosphorus acylating agent, and urea as the catalyst, glucose 1-phosphate was synthesized and its properties were analyzed. The synthesis conditions were selected according to the phosphorus content and optimized through the response surface methodology (RSM), based on a 3-level, 3-variable Box–Behnken experimental design.
4/5/2023 4:57:55 AM +00:00
Poly(4-vinylpyridine)-supported dual acidic ionic liquid: an environmentally friendly heterogeneous catalyst for the one-pot synthesis of 4,4’-(arylmethylene)bis(3-methyl-1-phenyl-1H-pyrazol-5-ols)
A poly(4-vinylpyridine)-supported Brønsted ionic liquid was easily prepared from its starting materials and used as a novel, highly efficient, and reusable heterogeneous catalytic system for the synthesis of 4,4’-(arylmethylene)bis(3- methyl-1-phenyl-1H-pyrazol-5-ols) from the condensation reaction between aromatic aldehydes and 2 equivalents of 3- methyl-l-phenyl-5-pyrazolone.
4/5/2023 4:57:29 AM +00:00
Ultrasound-assisted emulsification–solidified floating organic drop microextraction combined with flow injection–flame atomic absorption spectrometry for the determination of palladium in water samples
The ultrasound-assisted emulsification–solidified floating organic drop microextraction (USAE–SFODME) methodology was combined with flow injection–lame atomic absorption spectrometry (FI–FAAS) for the separation/preconcentration and determination of palladium at ultratrace level. In this method, the palladium ion in the aqueous solution was complexed with acetylacetone (6 × 10−3 mol L−1) in the pH range of 1–7 and was extracted into 40 µL of 1-undecanol, which was sonically dispersed in the aqueous phase.
4/5/2023 4:57:23 AM +00:00
Optimization of a gas chromatography–mass spectrometry method using chemometric techniques for the determination of ezetimibe in human plasma
A new, rapid, and sensitive gas chromatography–mass spectrometry (GC-MS) method was developed for the determination of ezetimibe (EZE) in human plasma. EZE was derivatized prior to GC-MS analysis. Various derivatization techniques such as acetylation, methylation, and silylation were tried. EZE was extracted from plasma with high recovery (94.39%–97.57%) using methyl tertbutyl ether and carbonate buffer (pH 9). Chromatographic conditions were optimized using chemometric methods.
4/5/2023 4:57:15 AM +00:00
Synthesis of novel benzimidazole salts and microwave-assisted catalytic activity of in situ generated Pd nanoparticles from a catalyst system consisting of benzimidazol salt, Pd(OAc) 2 , and base in a Suzuki-Miyaura reaction
Novel benzimidazolium salts having N-benzyl or N-(4-substitutedbenzyl) groups were synthesized and their microwave-promoted catalytic activity for the Suzuki–Miyaura cross-coupling reaction were determined using in situ formed palladium(0) nanoparticles (PdNPs) from a catalytic system consisting of Pd(OAc) 2 /K2CO3 in DMF/H2 O. PdNPs were characterized by X-ray diffraction (XRD) pattern and particle size of in situ generated PdNPs from the Pd(111) plane was determined to be of diameter 19.6 nm by the Debye–Scherrer equation.
4/5/2023 4:57:08 AM +00:00
Determination of zineb in tap water and tomato samples by adsorptive catalytic stripping voltammetry
This paper describes a sensitive and accurate adsorptive catalytic stripping voltammetric method for the determination of zineb (zinc ethylene-bis- dithiocarbamate) in tap water and tomato samples. The method is based on the reduction of adsorbed zineb at a hanging mercury drop electrode following its catalytic oxidation using peroxydisulfate as an oxidizing reagent. Chemical and instrumental parameters of the process were optimized.
4/5/2023 4:57:02 AM +00:00
Synthesis of 5-membered heterocycles using benzoylacetonitriles as synthon
This review article represents a survey covering the synthetic strategies leading to 5-membered heterocycles. The reactions are subdivided into groups that cover the synthetic methods of those heterocycles, i.e. pyrroles, furans, thiophenes, pyrazoles, isoxazoles, thiazoles, and others, utilizing benzoylacetonitriles as starting precursor from 1985 up to the present. The reactions are subdivided into groups that cover the synthetic methods for those heterocycles from benzoylacetonitriles.
4/5/2023 4:56:55 AM +00:00
Anticholinesterase furocoumarins from Heracleum platytaenium, a species endemic to the Ida Mountains
The petroleum ether extract of Heracleum platytaenium afforded 8 furocoumarins (psoralen, bergapten, xanthotoxin, pimpinellin, isopimpinellin, sphondin, byakangelicin, and heraclenol) and the methanol extract of H. platytaenium gave only 1 glycosylated dihydrofurocoumarin, apterin. In addition, stigmasterol was also obtained from petroleum ether extract. Structure identification of the isolated compounds has been achieved by using spectroscopic methods, namely 1D and 2D NMR experiments and mass spectral analyses.
4/5/2023 4:56:49 AM +00:00
Droplet condensation on polymer surfaces: a review
Dropwise condensation on substrates is an important topic of interest because it plays a crucial role in many scientific applications such as heat transfer, water harvesting from the humid atmosphere, and polymer templating. We focused on droplet condensation on polymer surfaces and briefly summarized the drop condensation studies reported in the last 2 decades and their potential applications.
4/5/2023 4:56:42 AM +00:00
(NHC)-Pd(II) complexes with hydrophilic nitrogen ligands: catalytic properties in neat water
The new complexes (1–3) were characterized by elemental analysis and spectroscopic methods and the molecular structure of 1a was determined by X-ray diffraction studies. These complexes were applied in the Suzuki–Miyaura cross-coupling reaction of phenylboronic acid with aryl halides in neat water. The activities of catalysts were monitored by gas chromatography–flame ionization detector and nuclear magnetic resonance. Whereas the complexes with DEA or 3-PCA ligands did not show significant difference in the activity, the BIAN-IPr complexes 1b and 3b bearing DEA and 3-PCA, displayed the highest catalytic activity at 100◦C.
4/5/2023 4:56:31 AM +00:00
Terpenoids, essential oil composition, fatty acid profile, and biological activities of Anatolian Salvia fruticosa Mill.
The essential oil, obtained from the aerial parts of the plant, exhibited high AChE inhibitory activity, consisting of mainly 1,8-cineol (58.89%). The antioxidant activity according to 6 complementary tests and anticholinesterase potential of the methanol extracts and triterpenoids α-amyryltetracosanoate, oleanolic acid, ursolic acid, and sitosterol acetate were also investigated, and methanol extract exhibited the highest antioxidant and anticholinesterase activity, surpassing the other tested extracts and pure compounds.
4/5/2023 4:56:24 AM +00:00
Synthesis of fused tetrazolone derivatives
New fused tetrazolone derivatives were synthesized using homophthalic and maleic anhydrides. Treatment of anhydrides with trimethylsilyl azide opened the lactone rings and formed the corresponding intermediates, which bore 1,3-dipole and dipolarophile functionalities in ortho positions. The intermediates partially underwent internal 1,3-dipolar cycloaddition to produce fused tetrazolone derivatives. When the carbonyl groups in anhydride were not conjugated with any double bond, then a triazine-fused tetrazolone derivative was formed.
4/5/2023 4:56:13 AM +00:00
Umpolung strategy: advances in catalytic C-C bond formations
This mini-review examines the recent advances in umpolung strategy, devised originally by Corey and Seebach. Although numerous stoichiometric variants have been published to date, this article covers just the catalytic C-C bond forming reactions due to their major benefits such as atom economy, less pollution, and workable simplicity. In the context of umpolung, the studies are evaluated under 3 main titles: enzyme, N -heterocyclic carbene, and cyanide ion catalyzed reactions. In particular, enzyme and NHC catalyzed reactions mainly involve asymmetric applications.
4/5/2023 4:56:06 AM +00:00