Cyclopropyl-containing sulfonyl amino acids: Exploring the enantioseparation through chiral ligand-exchange chromatography

Russian Journal of General Chemistry - In the scope of a broader study focused on glutamate receptors regulators, we have been engaged in synthesis, analysis and pharmacological characterization of...     

Preparation and optical properties of composite materials based on polybenzimidazole and silver nanoparticles

Rigid-chain heat resistant polymers (with poly-2,2'-p-oxydiphenylene-5,5′-bisbenzimidazole as example) were impregnated for the first time with a silver-containing precursor in formic acid and in supercritical carbon dioxide. A procedure allowing the precursor reduction to silver nanoparticles both throughout the volume by thermal annealing of the films in the temperature interval 100–150°С and in the targeted mode using lasers operating at 405 and 532 nm was developed. It opens prospects for developing a process for production of heatresistant optical gratings and light guides. The reduces nanoparticles and their agglomerates have the size in the interval 50–200 nm and give a plasmon band in the range 450–460 nm.     

Effect of the alkylidene spacer and the p-tert-butylthiacalix[4]arene macrocyclic platform on the reactivity of the hydroxyl groups in the acylation reaction

Russian Journal of General Chemistry - A series of cone and 1,3-alternate p-tert-butylthiacalix[4]arenes tetrasubstituted at the lower rim simultaneously by the amide, ester, and carboxyl functions...     

Synthesis of new phosphorylated analogs of nucleotides containing adenine and ethylidene-1,1-bisphosphoryl moieties

Reaction of adenine and 9-[2-(1,3-dioxolan-2-yl)ethyl]-9H-purine-6-amine with ethylidene-1,1-bisphosphonates resulted in the formation of new purine bases containing ethylidene-1,1-bisphosphoryl groups.

     

Solubilization of prothionamide with micelles of an amphiphilic acrylic acid oligomer with thiohexyl terminal groups and preparation of postoperative cavity filling formulations

An amphiphilic oligomer was prepared by telomerization of acrylic acid in the presence of n-hexyl mercaptan. The structure, molecular weight, critical micelle concentration, and ζ-potential of the oligomer, and also its particle-size distribution in aqueous solution were determined. The product allows solubilization of prothiondamide antituberculosis drug. A procedure was suggested for preparing a filling formulation containing prothionamide for filling postoperative cavities in connective tissue.     

Structure and Thermal Stability of Nanostructured Precursor Powders of Copper(I) Sulfide and Selenide

The hydrochemical precipitation method at 298 and 333 K with, respectively, thiocarbamide and sodium selenosulfate was used to obtain nanostructured powders of copper sulfide with formula composition Cu₂S, which are composed of globules 200–500 nm in diameter, formed by 70–100-nm particles, and copper(I) selenide, composed of crystallites with polyhedral shape, sizes of 80 to 500 nm, and a formula composition Cu_1.84Se. An X-ray diffraction analysis revealed the orthorhombic Cu₂S structure (space group no. 39-Abm2) with unit cell parameters a = 1.182 nm, b = 2.705 nm, and c = 1.343 nm. Powders of Cu_1.84Se copper selenide have a cubic structure (space group Fm3m) with lattice constant a = 0.5693 nm. A thermal analysis demonstrated that the chemically precipitated Cu₂S and Cu_1.84Se powders have a stable elemental composition up to 200–240°C. An intense oxidation of the samples begins at a temperature exceeding 250°C and is accompanied by a sharp decrease in their content of sulfur (selenium) and by an increase in the content of oxygen.     

Specific structural features of crystalline regions in biodegradable composites of poly-3-hydroxybutyrate with chitosan

Differential scanning calorimetry and X-ray diffraction at wide and small angles were used to examine the biodegradable composites of poly-3-hydroxybutyrate with chitosan, produced by mixing of these polymers in a rotor disperser at 150°C. Samples of individual polymers and composites with 80, 40, and 20 wt % poly- 3-hydroxybutyrate were studied. It was found that the presence of chitosan in the composites leads to a change in the crystallite size of poly-3-hydroxybutyrate and to an increase in the large period in this polymer. Mixing of poly-3-hydroxybutyrate with chitosan affects the structural rearrangement in crystalline regions of poly-3-hydroxybutyrate under a high-temperature treatment. The effect of a high-temperature treatment of the composites via alternation of melting–crystallization cycles in the nonisothermal mode, when a sample is heated and cooled at the same constant rate of 8 deg min–1 in the range from 20 to 200°C and is annealed at a temperature of 150°C, was analyzed. This analysis suggests that, in composites of this kind, the intermolecular interaction between the components is a factor strongly affecting the structure of the crystalline regions and the mechanism of their rearrangement in the course of annealing. The mechanism of this interaction is discussed.     

Distribution of Zinc Oxide Nanocrystals in a Polymer Film

The structure of polymer films modified with zinc oxide nanocrystals was studied by the optical absorption and small-angle X-ray scattering methods. Small-angle X-ray scattering allows determination of the nanoparticle size distribution function, which is the decisive factor in predicting the optical properties of heterophase materials, including filled polymer films. The optical absorption spectrum of an acrylate polymer film doped with 1.6 wt % zinc oxide nanocrystals approaches the ideal absorber spectrum, which allows this material to be recommended for use as a protective color filter.     

Effect of gas environment parameters on operation efficiency of chemical absorbents of carbon dioxide

Effect of main characteristics of the gas medium on the absorbing properties of alkaline chemical absorbents is demonstrated. The following gas flow parameters were examined as variables: carbon dioxide content of the gas flow within the range 0.2–5.0 vol %, gas humidity of 25–90 rel %, and pressure in the zone of the chemisorption process in the range from 2 to 6 MPa. As objects of study served mixed chemical absorbents based on calcium, sodium, and lithium hydroxides.     

Synthesis of basic bismuth(III) oxalate by precipitation from nitrate solutions

Conditions were determined in which basic bismuth oxalate of composition BiC₂O₄(OH) can be obtained by direct precipitation upon addition of oxalic acid from nitrate solutions used in production of bismuth compounds. The composition of the compound was confirmed by X-ray phase and chemical analyses, IR and Raman spectroscopy, and thermogravimetry. Electron microscopy was used to examine the effect of the composition of the reaction medium and temperature on the morphology of the product being obtained. It was shown that β-Bi₂O₃ can be obtained in oxidative thermolysis of basic bismuth oxalate, depending on its morphology.