Voprosy khimii i khimicheskoi tekhnologii (Issues of Chemistry and Chemical Technology)

4-9

Authors: L.S. Bobrova, V.S. Protsenko, F.I. Danilov

The paper reports the results of our experimental study on the effect of water content in a deep eutectic solvents containing a eutectic mixture of choline chloride (ChCl) and CrCl36H2O in the molar ratio of 1:2, respectively, on some physicochemical properties of liquid mixtures and electrochemical characteristics of the systems obtained. The density, viscosity and electrical conductivity of these liquid mixtures (i.e. ionic liquids) are measured in the temperature range of 25 to 80 С. It has been stated that the eutectic mixture under consideration (i.e. without extra water) is distinguished by an extremely high viscosity and a very low conductivity; thus, the practical use of this system for chromium electrodeposition has been called into question. The introduction of extra water is shown to promote a substantial increase in electrical conductivity and a decrease in viscosity and density of the mixtures ChCl + 2CrCl3 + xH2O, where x = 6, 9, 12, 15, and 18. The activation energies of conductivity and viscous flow are calculated; they diminish with extra water content. The obtained results are interpreted within the framework of the hole theory. The liquid systems with the water content corresponding to x = 12 or 15 allow electrodepositing uniform and well adherent chromium electrodeposits with a relatively high current efficiency (20-70%).

16-20

Authors: A.A. Ovcharenko, A.A. Golichenko, A.V. Shtemenko

Complex compounds of dirhenium(III), containing a unique quadruple metal-metal bond with low toxicity, have a number of useful biological properties, such as antineoplastic, antihemolytic, antiradical, hepato- and nephroprotective that stimulates the expansion of the range of such compounds due to the diversity of the ligand sphere. The aim of this work was the development of method for the preparation of complex compounds of dirhenium(III) with cystine. To obtain the target product, the reaction of (NBu4)2Re2Cl8 with cystine in a molar ratio of 1:10 was carried out under argon, in an acidic environment using a mixture of polar organic solvents (acetone – acetonitrile in the ratio of 4:1). Obtained substance after removal of solvent was recrystallized from ethyl acetate. The yield of product was 61%. This compound has a blue color, it was soluble in polar organic solvents and water, wherein the compound is stable over a long period of time. The composition and structure of the resulting compounds have been confirmed by elemental analysis, infrared and electronic spectroscopy, and the molar conductivity measurements. In the visible region of the spectrum the shift of the absorption band with 14700 cm-1 to 16670 cm-1 was observed, which corresponds to  electronic transition of rhenium-quad connection for rhenium complexes with the cis-position to the cluster bridging carboxylates Re26+. The substitution of acetonitrile to dimethylformamide as the axial ligand in cis-[Re2(Cys-Cys)Cl42CH3CN]Cl2 was studied. The possibility of obtaining the cluster compound of dirhenium(III) with cystine is one more step to the disclosure of the mechanism of biological action of binuclear cluster of rhenium(III).

26-31

Authors: O.V. Smirnova, I.V. Efimovа

To increase the efficiency of natural humic acids, their directed chemical modification seems to be rather perspective, the modification being associated with the introduction of new functional groups or the change of the number of groups which are present in the composition of the macromolecules. The application of directed chemical modification allows regulating surface-active, complexing, redox and other physicochemical properties of humic acids as well as their biological activity. In this paper, volumetric method was used to determine the antioxidant activity of humic acid and the products of their chemical modification in the processes of radical chain oxidation in an organic medium. The reaction of humic acids acylation by benzoyl chloride has been conducted under the condition of inversion trans-phase catalysis. The results of potentiometric titration showed that the interaction between humic acid and benzoyl chloride can occur via both hydroxyl (-OH) groups and carboxyl (-COOH) ones. We have determined the antioxidant activity coefficients for native and modified humic acids. The change in antioxidant activity of acylated humic acids in comparision with the baseline forms was stated which may be associated with a decrease in the number of active hydroxyl groups in the macromolecule structure by their binding as a result of chemical modification. It has been shown that the directed chemical modification of native humic acids may be a way to adjust their redox properties, this allows controlling the properties of natural substrates by means of the variation in the number of the functional groups in the macromolecules composition as a result of the acylation reaction.

36-39

Authors: E.N. Shved, M.A. Synelnikova, Yu.N. Bespal'ko

The kinetics and reaction scheme of the homopolymerization of ED-20 epoxy resin in the presence of amines with boron trifluoride complexes are proposed. It is shown that the complexes are decomposed under the action of epoxy resin with the release of amine and formation of new complex ED-20•BF3 at the initial stage of the process. The presence of the last one promotes two directions of reaction as follows: the first direction is a homopolymerization of ED-20, which is catalyzed by BF3, and the second direction is a curing of ED-20 by primary and secondary amines or the homopolymerization of ED-20, which is catalyzed by tertiary amines. The contributions of each direction depend on the amine nature. The cationic polymerization process of the resin under the action of BF3 (i.e. the first direction) competes with the curing process of the resin by highly basic primary and secondary amines (i.e. the second direction). In the case of the complexes of lowly basic primary and secondary amines as well as tertiary ones, the first direction makes a significant contribution to the rate of the process. Various directions of the interaction of amines with epoxy resin allow explaining a monotonic increase in the activity of the primary and secondary amines with an increase in the basicity (nucleophilic substitution reaction) and an abnormally low activity of tertiary amines (step-growths polymerization)

47-52

Authors: V. Budzinska, O. Slisenko, I. Bei

Organosilicate composites (OC) have been synthesized from polyisocyanate (PIC), aqueous sodium silicate and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane or (3-aminopropyl) triethoxysilane. Compatibility enhancement between immiscible urethane-based organic and silicate inorganic phases is provided by the addition of highly reactive organosilicon bifunctional coupling agents (CA). The features of the formation of organosilicate composites were studied in details by FTIR and thermogravimetry. It was stated that reactive silicon-based compatibilizers with amine and alkoxy functionalities act as coupling agents which can covalently combine both inorganic and organic phases of the composites. The formation of hybrid OC occurs via the chemical interaction of primary amine groups (or both primary and secondary ones) of CA with NCO groups of PIC, as well as alkoxy groups of CA with silanol groups of colloid polysilicic acid particles from sodium silicate solution. Appearing of urea moieties of polyureas during condensation reaction of isocyanate groups in a presence of water molecules was identified as well. Hybrid organosilicate composites are characterized by well-defined uniform structure resulted in appropriate thermal stability and improved physical-mechanical properties. The addition of CA drastically decreases curing time and substantially improves compression strength of obtained materials up to 50 MPa. The obtained hybrid materials have enhanced water resistance in comparison with unmodified ones and could be applied as sealants and protective coating for concrete based building materials.

60-64

Authors: O.S. Kabat, V.I. Sytar

We examined an aromatic polyamide – phenylone C2 which is a perspective polymer for various units of machines and mechanisms. This polymer is distinguished by enhanced physical-mechanical and thermophysical properties. However, a narrow temperature range of its processing into products limits the widespread use of the polymer. Therefore, an urgent task is to extend the temperature range of phenylone C2 processing and simultaneously maintain the enhanced complex of its properties. This task has been accomplished via the creation of composite materials based on phenylone C2, fine-dispersed titanium and silicon dioxides. The introduction of these fillers leads to an expansion of the processing temperature range up to 10-15 C and to an increase in the optimal temperature of processing of the composites based on phenylon C2 (up to 5-10 C). The mechanical and thermophysical properties of the composites obtained are close to those typical of basic polymer.

70-76

Authors: S. Oparin, L. Holyavchenko, S. Davydov

The paper reports the evaluation criteria and computational procedure of the performance parameters of the plasma gasification process in carbon-containing media. This method allows determining parameters of the gasification process at various temperatures and establishing their optimum values on the basis on the composition carbonaceous media and the type of gasification process. The temperature dependences of qualitative and quantitative indicators of the coal gasification process are given, they being obtained as a result of the thermodynamic calculations. The optimum temperature of the process of steam-plasma gasification is close to 1700-1800 K at which a maximum output of gas is observed. The dependences of specific energy consumption of coal gasification process on the process temperature are established on the basis of the calculations performed by means of the developed method for determining the performance parameters. The specific power input in terms of coal consumption and the volume power input are 3.16 kWh/kg and 0.933 kWh/m3, respectively, when the process of steam-plasma gasification is carried out at the temperatures of 1700 to 1800 K. The method of calculating the production cost of gas synthesized by steam-plasma gasification is reported.

82-88

Authors: O.V. Savvova, O.V. Babich, A.O. Gryvtsova

The main trends in development of glass-ceramic materials on the basis of lithium aluminosilicate glasses have been analyzed in this work; the availability of their use as elements of personal armor protection has been established. Considering the complex of requirements to glass-ceramic materials, we choose the system and synthesized the compositions of model glasses in the R2O–LiF–CaF2–RO–RO2–R2O3–P2O5–SiO2 system (where R2O = Na2O, Li2O or K2O; RO = СaO, MgO, ZnO or MnO; RO2 = ZrO2, TiO2, SnO2 or CeO2; R2O3 = Al2O3 or B2O3). The mechanism of phase formation on the developed lithium aluminosilicate glasses has been determined which consists in fine volume crystallization with the formation of β-spodumene in the materials during thermal treatment. It has been established that low-temperature pre-crystallization of lithium metasilicate under the conditions of two-stage thermal treatment allows forming glass-ceramic structure of materials which is a prerequisite for their high strength. The data obtained may be used for developing glass-ceramic materials for personal armor protection elements.