French-Ukrainian Journal of Chemistry
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Thermochemical properties and glass forming tendency modeling for the ternary Ge–Mn–Gd melts
Get PDFInformation on the thermochemical properties may be useful for predicting of the concentration regions of easy glass formation in multicomponent alloys. In present investigation the integral enthalpies of mixing for the Ge–Mn–Gd melts were determined for the entire concentration interval at 1830 K using the Redlich-Kister-Muggianu method. GFT values for binary and ternary alloys of this system were calculated. Size mismatch entropy was estimated within the frameworks of hard spheres model. On the basis of performed calculations the concentration regions in which the melts of the Ge–Mn–Gd system can demonstrate considerable tendency to easy glass formation were suggested
Catalytic efficiency of activated carbon functionalized with phosphorus-containing groups in 2-propanol dehydration
Get PDFThe functionalization of activated carbon (AC) by P-containing groups was conducted, and their thermal desorption was studied. Depending on the used method, the functionalized AC contains 0.5–1.45 mmol/g of acidic groups acting in catalytic 2-propanol dehydration. All catalysts showed 100% conversion of 2-propanol to propylene. The catalytic activity does not change with time under isothermal conditions and during their repeated use in catalysis, for 3 cycles of heating-cooling. In fact, the yield of propylene remains stable; it does not decrease with each cycle. Preliminary oxidation with nitric acid causes a small increase in the catalytic activity
Influence of water-soluble nonionic polymers adsorption on colloidal properties of nanosilica dispersions
Get PDFThe relationships between the adsorption of poly(vinyl alcohol) (PVA), poly(ethylene oxide) (PEO), and poly(vinyl pyrrolidone) (PVP) of various molecular weights onto nanosilica and the stability and rheological properties of the aqueous dispersions were analyzed. The adsorption isotherms for the polymers correspond to the Langmuir-type isotherms. The adsorption maximum slightly increases with increasing molecular weight of the polymers. The sedimentation and aggregative stability of the silica dispersion decreased at a low amount of an adsorbed polymer (less than a monolayer). At this polymer content, a significant increase in the viscosity of dispersions is observed due to the formation of polymeric bridges between silica nanoparticles from neighboring aggregates of them. If the amount of adsorbed polymer exceeds the monolayer then the stabilizing effect is observed due to the steric factor preventing the bridge formation and the viscosity of dispersion decreases slightly compared with systems with a low polymer content
Thermodynamic properties of methyl 4-(4-methoxyphenyl)-6-methyl-2-oxo-1,2,3,4-tetrahydropyrimidine-5-carboxylate in organic solutions
Get PDFThe enthalpy and the entropy of dissolution of methyl 4-(4-methoxyphenyl)-6-methyl-2-oxo-1,2,3,4-tetrahydropyrimidine-5-carboxylate in 2-propanol, ethyl acetate, acetonitrile, 2-propanone and benzene were determined from the temperature dependence of its solubility.The enthalpies and the entropies of mixing at 298 K were calculated taking into account the enthalpy of melting of the compound, determined via differential thermal analysis.The influence of the solvent on the solubility of the compound and on the corresponding enthalpy and entropy of mixing values was shown
Hybrid-stabilized silver nanoparticles and their biological impact on hospital infections, healing wounds, and wheat cultivation
Get PDFThe structure and morphology of new biocide compositions based on silver nanoparticles and silica/polyacrylamide hybrids, as well as their diverse biological effects on traditional hospital infections and wound healing and winter wheat cultivation, were studied. The compositions showed a high bactericidal effect against bacteria of the genera Staphylococcus and Pseudomonas, and fungistatic effect against the yeast genus Candida and filamentous fungi of the genera Aspergillus, Cladosporium, Penicillium, Exophiala, and Fusarium. They also showed high activity in wound healing in rats and significantly changed the rate of development of winter wheat plants due to presowing treatment of seeds
Chemical grafting of sulfo groups onto carbon fibers
Get PDFWe proposed the brominated carbon cloth that made of polyacrylonitrile-based activated carbon fibers (PAN-ACFs) as a precursor to chemically and uniformly graft SO3H groups to prepare the solid acid catalyst. The thermal and catalytic properties of the sulfonated PAN-ACFs were examined by IR controlled catalytic measurements and thermal analysis. The catalytic test results showed that the sulfonated surface remarkably improved the operating efficiency in isopropanol dehydration by decreasing the reaction temperature. All PAN-ACFs with grafted SO3H groups prepared through brominated precursors can converse 100% of isopropanol into propylene at moderate temperature. They showed the highest catalytic activity compared to PAN-ACFs sulfonated with oleum and chlorosulfonic acid, which conversed only 40% and 70% of isopropanol into propylene and deactivated at the higher temperatures in the reaction medium
New N-difluoromethylindoles: features of N-difluoromethylation of indoles with electron-donor or electron-withdrawing substituents
Get PDFThe study of the difluoromethylation of various indole derivatives containing both electron-donating and electron-withdrawing groups was carried out. N-Difluoromethyl derivatives of indole with methoxy, methyl, nitro, cyano, amino groups and bromine atom were isolated and fully characterized
Synthesis of masked 2-amino-6-methyl-4-oxo-4H-pyran-3-carbaldehydes
Get PDFAcetoacetylation of (1,3-dimethylbenzimidazol-2-ylidene)-, (3-methylbenzothiazol-2-ylidene)-, and (3,4-dimethylthiazol-2-ylidene)acetonitriles with 2,2,6-trimethyl-4H-1,3-dioxin-4-one was found to yield appropriate C-acylation products. Treatment of the obtained products with perchloric acid afforded 2-(2-amino-6-methyl-4H-pyran-4-one-3-yl)substituted quaternary azolium salts. Their reduction with sodium borohydride yielded the corresponding dihydro (in the case of benzoazoles) or tetrahydro (in the case of thiazole) derivatives, which were shown to be synthetic equivalents of the title aldehyde
6-Oxyindan-1-ones with amino acid fragments
Get PDFNew indan-1-one derivatives (8 examples) with amino acid fragments were synthesized through the N-acylation of the amino acids by 2-(3-oxo-2,3-dihydro-1H-inden-5-yloxy)acetic acid using the method of activated N-hydroxysuccinimide esters. To obtain corresponding methyl esters (2 examples) two ways were possible: the N-acylation of the amino acid methyl esters by 2-(3-oxo-2,3-dihydro-1-inden-5-yloxy)acetic acid through the activated imidazole derivatives or methylation of the carboxylic function of preformed N-{[(1-oxoindan-6-yl)oxy]acetyl}amino acids
Investigation of the reaction mechanism of [4 + 2] cyclization of 2,3 dimethylbuta-1,3-diene to methylacrylate using the Michaelis-Menten equation
Get PDFThe cycloaddition reaction between 2,3‑dimethylbuta-1,3-diene and methylacrylate proceeds by the second order kinetics. The rate constants increase with the increase in the excess of one of the reactants. The change in the effective rate constants is described by the Michaelis–Menten equation indicating that the reaction proceeds through the initial equilibrium stage of formation of a molecular complex stabilized by van der Waals interaction which then transforms into the product. The limiting stage of the reaction is established and its mechanism is suggested