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

20-25

Authors: A.P. Avdeenko, S.A. Konovalova, I.Yu. Yakymenko

Indole derivatives are an essential elements of many natural and synthetic compounds having significant biological activity. New derivatives of 2,3-dimethylindole were synthesized in this work by the reaction of N-(4-oxocyclohexa-2,5-dien-1-ylidene)arylsulfon(aroyl)amides and 4-methyl-N-(4-oxonaphthalen-1(4H)-ylidene)benzene-1-sulfonamide with 2,3-dimethylindole. The possibility of these reactions is determined by the redox potential of the starting amides and steric factor. If there is a free C=C bond in the quinoid ring of the starting arylsulfonamides, the reaction proceeds under the 1,4-addition scheme with the formation of corresponding N-[3-(2,3-dimethyl-1H-indol-1-yl)-4-hydroxyphenyl(naphthyl-1)]arylsulfonamides which are potentially biologically active compounds. N-(4-Oxocyclohexa-2,5-diene-1-ylidene)aroylamides have a high redox potential as compared with similar arylsulfonamides and naphthalene derivatives; therefore, two processes proceed in their reaction with 2,3-dimethylindole: reduction and 1,4-addition. The 1,4-addition product was obtained only for the 2,3-dimethyl derivative, which has the lowest redox potential among the investigated aroylamides. Analysis of the potential biological activity of the synthesized compounds by using the PASS program showed that the synthesized products can exhibit the following activities: para amino benzoic acid antagonist, glutamyl endopeptidase II inhibitor, CYP3A2 substrate, insulysin inhibitor, membrane integrity agonist and phobic disorders treatment.

33-37

Authors: V.I. Goleus, T.I. Nahorna, R.I. Kyslychna, S.Yu. Naumenko

It is known that enamel coatings with enhanced protective and decorative properties can be fabricated on the basis of boron-silicate glass frits with an increased content of TiO2 in their composition. Opacity and white color of enamel coatings are due to their crystallization at firing temperatures. Titanium glass enamels are not pure white visually, and show yellow and blue shades depending on their chemical composition. The purpose of this work was to establish the influence of basic components on the water resistance and color characteristics of titanium enamel coatings. Our experimental study was focused on the glass frits with the chemical composition described by the generalized formula (76–n–m)SiO2nB2O3mNa2O24MexOy, where MexOy is the total content of TiO2, ZrO2, Al2O3, MgO, СaO, P2O5, and K2O. It was found that the glass frits with the following content of basic components (mol.%): Na2O 12–13, K2O 3, B2O3 10–11, SiO2 49–51 demonstrated the highest water-resistant properties. The color characteristics of titanium enamel coatings prepared on the basis of the mentioned glass frits differ significantly from the reference white light A; the titanium enamel coatings under consideration have a yellow-green tint. The highest deviations of the enamel coating color purity and color tone from a standard of white color were observed when increasing the Na2O content in the glass frits composition at the expense of SiO2. The color of titanium coatings with the highest water resistance has a deviation from the standard of white color within 4–6%.

44-49

Authors: O.M. Dykun, V.M. Anishchenko, A.M. Redko, V.I. Rybachenko

To understand deeply the process of acylation of natural polyphenol gossypol, its stepwise benzoylation was performed using benzoyl chloride and benzoic anhydride as acylating agents in the presence of pyridine-N-oxides. The influence of the composition of a reaction mixture on the benzoylation process and reaction products was analyzed by the method of reversed-phase high-performance liquid chromatography. It was established that benzoylation of gossypol leads to the tautomeric transition of the respective fragment from aldehyde to lactol tautomeric form. This transition is most likely due to the breaking of the hydrogen bond C(7)–OHO=C(11) in combination with the displacement of the aldehyde group by the benzoyl fragment from the naphthyl ring plane (in the case of benzoylation of C(7)–OH group); benzoylation of C(6)–OH group is accompanied by the breaking of the hydrogen bond C(6)–OHO–C(7). These changes of configuration significantly facilitate the proton transfer from the C(1)–OH group to oxygen at C(11) followed by the formation of the lactol cycle. The use of benzoyl chloride as an acylating agent in combination with triethylamine and 4-methoxypyridine-N-oxide allows benzoylating gossypol quickly. However, the variety of formed benzoates is quite large because of the similar reactivity of different hydroxyl groups. In the case of benzoic anhydride, the number of isomeric gossypol benzoates remains quite high. Much more esters with higher retention time are accumulated due to a higher degree of benzoylation.

59-68

Authors: K.V. Kalafat, N.A. Taran, V.P. Plavan, A.M. Redko, I.V. Efimova, L.M. Vakhitova

In order to optimize the formulation of fire protective coatings for metal constructions, the effect of the ratio of main components in an intumescent system "ammonium polyphosphate–melamine–pentaerythritol" on the thermal destruction of the coating under conditions of fire (200–8000C) has been investigated. Thermal transformations of coatings were studied both by thermogravimetry with stepwise determination of the expansion coefficient by temperature variation and by IR spectroscopy. It was established for the first time that the ratio of ammonium polyphosphate, melamine and pentaerythritol as well as their content in the intumescent system is a factor determining the limit of the fire resistance of steel constructions, which a fire protective coating can ensure. Intumescent coatings with an ammonium polyphosphate:melamine:pentaerythritol ratio of 2:1:1 were shown to be more effective ones to provide the fire resistance of a steel construction during 30 minutes (R30). In turn, the use of the above ratio of 3.5:1:1.5 can provide the limit of the fire resistance of steel construction during 60 minutes (R60). The mixture of melamine and dicyandiamide in the intumescent system causes a synergistic effect, which leads to a non-additive increase in the fire protective efficiency of the coating. The results of this study have been confirmed by full-scale fire tests; they may be used to develop effective means of fire protection of steel constructions.

75-82

Authors: L.O. Kernosenko, Yu.M. Samchenko, N.O. Pasmurtseva, O.V. Legenchuk, T.P. Poltoratska

The characteristics of a hybrid pH-sensitive hydrogel sorbent based on polyvinyl formal and polyacrylic acid, synthesized by radical copolymerization, were investigated in the process of removing copper (II), zinc (II) and nickel (II) metal ions from water solutions. A high efficiency of the extraction (up to 96%) of metal cations (Cu(II)>Zn(II)Ni(II)) was reveled at their concentration of up to 250 mg L–1 in the pH range of 5.8 to 6.8. The experimental data were analyzed by using theoretical kinetic models and adsorption isotherms. The developed polymer sorbent was shown to be promising for removing heavy metals, even after its multiple regeneration.

91-98

Authors: O.Yu. Makido, Yu.G. Medvedevskikh, G.I. Khovanets

The catalytic oxidation of organic substances, in particular by the Fenton method, is one of the effective methods of wastewater treatment. The oxidation efficiency is affected by the adsorption properties of the catalyst when using heterogeneous catalysts in the Fenton process. In this work, the adsorption kinetics of methylene blue dye from aqueous solutions of different concentrations on the surface of the synthesized nanostructured magnetosensitive catalyst CoFe2O4/SiO2/CoMnO2 was studied by spectrophotometric analysis and the kinetic parameters of the process were determined. The CoMnO2-based "core–shell" catalyst has a magnetically sensitive cobalt ferrite core coated with a protective layer of porous SiO2, on the surface of which clusters of cobalt and manganese oxides are placed as catalytic centers. The process of adsorption of methylene blue from an aqueous solution can be considered as a quasi-chemical reaction of displacement of solvent molecules from the adsorption layer by dye molecules. The equilibrium state is described by the Langmuir equation, in which the effective adsorption constant is the ratio of the equilibrium constants of the Langmuir interactions of the dye and the solvent, respectively, with the active center of the adsorbent. The limiting adsorption of methylene blue and the adsorption constant characterizing the affinity of the dye to the catalyst surface were determined. The specific area of the catalyst was calculated under the condition of a known landing plane of the dye molecule. The influence of the adsorption properties of the catalyst on the efficiency of the Fenton process was established.

106-114

Authors: B.F. Minaev, V.A. Minaeva, O.O. Panchenko, S.V. Bondarchuk

Density functional theory calculations for p-Br-N-sulfinylaniline and m-nitro-N-sulfinylaniline in the ground singlet (S0) and triplet (T1) excited states are presented and analyzed in terms of their specific physicochemical properties. As all aromatic N-sulfinylamines, these compounds are rather unstable being sensitive to moist air and we assign this instability to the thermally allowed S0T1 excitation induced by internal magnetic forces. Our calculations indicate that the T1–S0 energy gap in these molecules is unexpectedly low and spin-orbit coupling matrix element between these states is relatively high, being allowed by the orbital symmetry selection rules. We also apply the exchange mechanism of spin-catalysis concept in order to explain the prone of N-sulfinylamines to the Diels-Alder cycloaddition with dienes.

124-133

Authors: M.V. Nikolenko, K.V. Vasylenko, V.D. Myrhorodska, I.M. Ryshchenko

For the first time, a linear correlation was found between the specific solubility products of calcium orthophosphates and their molar ratio Ca/P (the correlation coefficient being R2=0.9742). Nevertheless, the values of solubility products of tricalcium phosphate (pKS=26–29), hydroxyapatite (pKS=116.8) and its Ca-deficient forms (pKS~85) cannot be correlated. We proposed to adjust these values of solubility products in accordance with the obtained correlation dependence as follows: pKS is 40, 155 and 114–155 for tricalcium phosphate, hydroxyapatite and Ca-deficient hydroxyapatite, respectively. The calculated solubility diagrams (isotherms) with adjusted solubility products agree reasonably well with the known experimental data, which could not be explained and were not accepted by the scientific community up to the present day. Based on well-known ideas of chemical thermodynamics, we suggested an explanation of the correlation between the specific solubility products of calcium orthophosphates and their molar ratios Ca/P. The developed model of dissolution process is based on a comparison between crystal lattice energy and hydration energy of calcium ions. The experiments on chemical precipitation of orthophosphates were performed at pH 4–10 and at a constant molar ratio Ca/P=1.5; their results showed that only one single metastable form, calcium hydrogen phosphate, is precipitated within the entire pH range at the temperature of 200С. The obtained sediments were isothermally exposed at the temperature of 2500С in a mother solution for 6 hours; such a treatment resulted in a full dehydration of calcium hydrogen phosphate and its partial transformation into a more stable form (hydroxyapatite). The mass fraction of hydroxyapatite increases from 14% to 70% and the degree of crystallinity decreases from 20% to 5% with increasing the value of solution pH. It was concluded that the rate of phase transition from CaHPO4 to Ca10(PO4)6(OH)2 in influenced by the concentration of hydroxide ions that are incorporated into a crystal lattice of hydroxyapatite.

142-150

Authors: M.V. Petlovanyi, S.A. Zubko, V.V. Popovych, K.S. Sai

The strength and microstructural properties of the backfill massif have been studied and assessed when filling underground cavities that pose a threat of mine rocks collapsing in the process of mining mineral deposits. It is suggested that due to a tendency to mechanical destruction by crushing Ca–O ionic bonds rather than Si–О covalent ones, the backfill mixture composition is saturated with a large amount of Ca2+ ions. This leads to the formation of a highly-basic type of hydrated calcium silicates and a decrease in the massif strength properties. To study the mineral composition of the components of the mixture and solidified massif and to investigate the microstructure and chemical composition of new formations in the backfill massif, infrared spectroscopy and scanning electron microscopy were used. Laboratory studies of the strength properties of backfill massif were also conducted. The minerals of the mixture components, melilite and pseudowollastonite, have been revealed that perform the main function of the new formations occurrence. It was found that the strength of the backfill massif is by 16% less than the required standard value of 7.0 MPa at the age of 90 days. It was determined that highly-basic jellylike hydrated silicates of tobermorite type of the group CSH (II) with variable composition and a ratio of CaO/SiO2=2–3 are formed in the studied structure of the backfill massif after 90 days of hardening. There are no strong low-basic hydrated calcium silicate bonds that could have a reinforcing effect. Providing the conditions for occurrence of low-basic hydrated calcium silicates in the structure is one of the ways to create a hard backfill massif.

159-164

Authors: I.I. Seifullina, E.E. Martsinko, E.A. Chebanenko, V.V. Dyakonenko, S.V. Shishkina, А.G. Pesaroglo

A novel synthesis method was developed which allows isolating a new coordination compound with polymeric structure {[Ge2(OH)2(3-hpdta)2Cu2(bipy)2]2Н2О}n (І) (where hpdta5– – anion of 2-hydroxy-1,3-diaminopropane-N,N,N',N'-tetracetic acid, bipy – 2,2'-bipyridine) in solid state. Elemental composition, features of thermal decomposition, and molecular and crystalline structure of the synthesized complex were established. According to the data of X-ray diffraction analysis, complex I is a coordination polymer. The polymer chain is formed due to the bridging function of deprotonated ligands hpdta5–, which are simultaneously coordinated with germanium and copper atoms. Ge(1) and Ge(2) atoms have the same coordination environment and distorted octahedral polyhedrons. The coordination polyhedron of Ge(2) is formed due to the coordination of oxygen atoms of two carboxylate and one deprotonated hydroxyl groups of one ligand hpdta5–_1 and carboxylate group of the second ligand hpdta5–_2 in the equatorial direction. In the axial direction, the Ge atom coordinates with the nitrogen atom of the ligand hpdta5–_1 and the hydroxo-ligand. The coordination polyhedrons of Cu(1) and Cu(2) are square pyramids, in which molecules of bipy are coordinated with Cu2+ by two nitrogen atoms. One nitrogen atom and one oxygen atom of the carboxylate group of the hpdta5– ligand are located in the base of a square pyramid. In the apical direction, copper coordinates with deprotonated hydroxyl group of the same hpdta5– ligand. A –-stacking interaction was detected in the crystal between the -systems of bipyridines of two neighboring coordination polymer chains directed along the crystallographic axis a that form double chains with the cavities of 623.04 Å3.

171-178

Authors: O.B. Tselischev, S.O. Kudryavtsev, M.G. Loriya, S.V. Boychenko, V.G. Lanetsky, I.V. Matveeva, S.V. Leonenko, M.A. Tselishcheva

The article presents the results of the study on the influence of bioethanol content and parameters of cavitation field on the octane number of motor natural gasoline. The effects of the parameters of cavitation field on the modification of fuel and the changes of qualitative and quantitative composition of gasoline were investigated. The influence of the content of a biocomponent on the increase in the octane number was established. It was stated that the problem of the phase separation in alcohol-gasoline mixture can be solved by means of dynamic cavitation. The paper presents the results of the study of the change of octane number as a function of the intensity of cavitation treatment for gas condensate gasoline with addition of bioethanol. The physical stability of gas condensate and bioethanol mixture after cavitation treatment is investigated. It was shown that the gas condensate gasoline modified with bioethanol and cavitation field can be used as a high-quality motor gasoline. It was stated that low-octane gas condensate gasoline can be transformed into high-quality motor fuel by means of modification with bioethanol in the cavitation field. It was established that the alcohol-gasoline cavitation treatment leads to the homogenization and provides at least 30 days' mixture stability before separation. With increasing bioethanol content in the mixture, the number of cavitation cycles (intensity) required to achieve a constant octane number value decreases from 8 cycles for gas condensate gasoline without bioethanol to 4 cycles at the content of bioethanol of 3% and above.