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Chemical Bulletin of Kazakh National University
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  This is an Open Access Journal Open Access journal
ISSN (Print) 1563-0331 - ISSN (Online) 2312-7554
Published by Al-Farabi Kazakh National University Homepage  [2 journals]
  • Synthesis of the S/AgBr nano/micropowder in DMSO-water system

    • Authors: Natalya V. Khan
      Pages: 4 - 10
      Abstract: A new synthesis method of S/AgBr nano/micropowder based on sulfur and silver halide was developed. The nano/micropowder was obtained in the DMSO-water system, in two stages. Initially, sulfur was dissolved in DMSO at 120°C. The resulting solution was cooled to room temperature and separated from sulfur by filtration. Then, pre-prepared water solutions of AgNO3 and NaBr were introduced drop by drop into a sulfur solution in DMSO, at room temperature. The phase composition and structure of the precipitated powdery sediment were studied by X-ray diffraction analysis (XRD) and Raman spectroscopy. Scanning electron microscopy (SEM) was used to study the morphology and particle size. XRD showed the presence of the crystalline phase of AgBr, while the Raman spectra were characterized by the presence of sulfur and AgBr peaks. The SEM results showed that the S/AgBr is represented by oval, spherical and triangular particles of a homogeneous structure; the particle size was in the range from 300 to 800 nm.
      PubDate: 2022-01-21
      DOI: 10.15328/cb1254
      Issue No: Vol. 104, No. 1 (2022)
  • Composition based on alicyclic copolymide and polyethylene terephthalate

    • Authors: Maira B. Umerzakova, Rahima B. Sarieva, Asylbek A. Yespenbetov, Zhaniya N. Kainarbayeva
      Pages: 12 - 21
      Abstract: The addition of polymers such as polyethylene terephthalate, polycarbonate and polyurethane to another high molecular weight compound often provides improvement of properties of initial polymerfilms. These compounds can be successfully applied for obtaining of composite films based on polyimides. In the present work, conditions of making polymer composite films with arylalicyclic structured copolyimides and influence of polyethylene terephthalate on them were studied. It was found that, addition of component from 0.5 to 2 wt.% provides retaining of the polymers’ compatibility in the composite. Films formed from solutions of these compositions are transparent, brittleness of the material is not observed and there were little changes in elasticity compared with original copolyimide film. FTIR studies showed that the formation of these polymer blends leads to the interaction of functional groups of the polymers with hydrogen bonds, which determine the blend components compatibility. It has been found that, upon additional heat treatment of the films no more than 250°C, intermolecular crosslinking partially occurs with formation of an oxygen bridge between the amide acids of copolyimide and the added component. Such crosslinking provides increase of heat resistance and strength of the film. It should be noted that, for carrying out extensive research, it is preferable to use a simple method of mechanical mixing for components.
      PubDate: 2022-01-21
      DOI: 10.15328/cb1248
      Issue No: Vol. 104, No. 1 (2022)
  • Thermoconversion of ethanol on Al2O3 and SiO2 oxides

    • Authors: Manshuk M. Mambetova, Gaukhar Ye. Yergaziyevna, Kusman Dossumov
      Pages: 22 - 29
      Abstract: This work is devoted to the study of the catalytic properties of Al2O3 and SiO2 in the process of thermal conversion of ethanol, as well as to the determination of the acid characteristics of these oxides The catalytic properties of oxides in the thermal conversion of ethanol were studied in a flow-through mode at a reaction temperature of 250°C and a space velocity of 0,5 h-1. The acidic characteristics of the Al2O3 and SiO2 oxides were determined by the method temperature-programmed desorption of ammonia (TPD-NH3).  It has been established that the process of thermal conversion of ethanol includes the reactions of dehydration, dehydrogenation and dimerization. During the thermal conversion of ethanol on aluminum and silicon oxides, a dehydration reaction occurs with the formation of diethyl ether, with concentrations of 24,5 vol. % on Al2O3 and 19,6 vol. % on SiO2. It was determined that in parallel with the reaction of ethanol dehydration, its dehydrogenation with the formation of acetaldehyde takes place, but with a lower selectivity compared to dehydration. It was found that on Al2O3, which has a lower acidity in comparison with SiO2, the deformation of acetaldehyde occurs with the formation of butanol.
      PubDate: 2022-01-21
      DOI: 10.15328/cb1227
      Issue No: Vol. 104, No. 1 (2022)
  • Synthesis, structure and mechanical properties of composite hydrogels for
           medical use

    • Authors: Galymzhan K. Mamytbekov, Zhomart I. Bekultanov, Valentina I. Bannykh
      Pages: 30 - 42
      Abstract: The mechanism of formation of slightly crosslinked composite hydrogels based on natural agar-agar polysaccharide, synthetic polymers for medical purposes – poly-N-vinylpyrrolidone (PVP) and low-molecular plasticizers (polyethylene glycol PEG-400 and glycerin) synthesized by electron irradiation was considered from the point of view of analyzing their mechanical characteristics under various types of applied efforts. It is established that the synthesis conditions and the component composition of the initial mixture determine the formed structure of the hydrogel compositions and their mechanical properties. A new interpretation of the formation of the structure of composite hydrogels in the presence of various plasticizers is given. A detailed analysis of the deformation curves of composite hydrogels is presented taking into account the elastic-elastic, highly elastic and forced-elastic states.
      PubDate: 2022-03-13
      DOI: 10.15328/cb1264
      Issue No: Vol. 104, No. 1 (2022)
  • Stereocontrolled intramolecular transformations of (-)-α santonin

    • Authors: Amantay N. Iskanderov, Pavel Vojtisek, Saltanat K. Zhokizhanova, Aktoty A. Jadenova, Nurlan Merkhatuly
      Pages: 44 - 49
      Abstract: Chemical transformations of eudesmane sesquiterpene γ-lactones, leading to new biologically active compounds, have become an important direction in medicinal chemistry. This article discusses the stereoscopic intramolecular transformations of the sesquiterpene γ-lactone of the eudesmanic structure (-)-α santonin, a perspective natural compound characterized by a wide spectrum of biological activity.Stereoselective synthesis of new practically significant cis-condensed keto-eudesmane esters and ethylated santonin derivatives was carried out at room temperature in an argon atmosphere by the reaction of α-santonin with methyl and ethyl alcohols and alkyl halides in the presence of the Me3CONa-DMF base. It was revealed that, under the reaction conditions, the initial stage of santonin carbanion formation initiates subsequent stages of intramolecular electrophilic rearrangements with the formation of anenolate ion, which futhur interacts stereoselectively with nucleophilic and electrophilic reagents.It was shown that the synthesis of C4-α-ethyl-santonin with a six-membered ring configuration in the form of a distorted chair-chair can serve as a confirmation of the proposed mechanism of formation of practically valuable 6-keto-eudesmane ethers. In this article, the structure and spatial structure of the synthesized compounds is established using modern physicochemical and spectroscopic (1H NMR, 2D COZY NMR, NOESY, mass-spectrometry and X-ray structural analysis) research methods.
      PubDate: 2022-01-21
      DOI: 10.15328/cb1251
      Issue No: Vol. 104, No. 1 (2022)
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