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

8-17

Authors: A.V. Knishevitsky, N.I. Korotkikh, T.M. Pekhtereva, I.A. Krasnorutsky, O.P. Shvaika

The novel carbenoid salts were synthesized by the interaction of sterically hindered dialkyl- and diarylformamidines with epichlorhydrin and diiodopropane, these carbenoid salts being precursors for six-membered diaminocarbenes 5,6-dihydro-4H-pyrimidine-2-ylidenes comprising 1-adamantyl, mesityl and 2,6-diisopropylphenyl substituents. The representatives of a new series of carbene and acetonitrile adducts (i.e. cyanomethylazines) were obtained by means of the deprotonation of the salts mentioned above by sodium hydride in acetonitrile. The applicability of cyanomethylazines for obtaining copper carbene complexes was demonstrated in a reaction of 1,3-dimesityl-2-cyanomethylhexahydropyrimidine with copper(I) chloride. The novel diaminocarbene copper(I) and silver(I) complexes were obtained by the interaction of 5,6-dihydro-4H-pyrimidinium salts with silver(I) oxide and copper(I) iodide in the presence of potassium tert-butoxide.

22-29

Authors: N.V. Lutsenko, M.O. Mironyak, V.I. Tkach

The reaction of the interaction of diterpene steviol glycosides with heteropolyanion PMo12O403- is investigated in this communication by UV spectroscopy and amperometric titration. The slightly soluble associate which has been formed was used as an electrode active substance in the improved membranes of ionselective electrodes, convertible to organic cationic part stevioside-Ba2+. The methods of amperometric titration and direct potentiometric determination of the amount of diterpene glycosides in aqueous Stevia Rebaudiana extracts are offered, they are highly sensitive, selective and accurate.

34-39

Authors: O.Yu. Pankina, N.I. Korotkikh

The pathways of interaction between 5-aminoderivatives of benzimidazol-2-one and acetoacetic ester (i.e. Conrad-Limpach reaction) and acetylacetone (i.e. Combes reaction) are studied in this work depending on the reaction conditions. The intermediate aminocrotonates and enaminoketones are cyclized into 2-oxoderivatives of imidazo[4,5-f]quinolines in diphenyloxide or into imidazo[4,5-g]quinolines in polyphosphoric acid. This result may be explained by the fact that aminocrotonates exist as H-chelates in neutral medium of diphenyloxide in which a crotonate fragment is close to the most nucleophilic fourth atom of the condensed ring. In polyphosphoric acid, such complexes are broken and more thermodynamically stable line condensed compounds are formed. It was also found that intermediate aminocrotonates are cyclized into imidazo[4,5-f]-quinolin-2,9-diones and imidazo[4,5-g]quinolin-2,8-diones derivatives that has been confirmed by NMR- and IR-spectroscopies and quantum chemical calculations.

43-47

Authors: G.M. Rozantsev

A chemical model of isopolyniobate anions formation in aqueous solution with the initial niobium concentration of 10-4 M was proposed on the basis of the pH-potentiometric titration experimental data and using the mathematical modeling method (the software CLINP 2.1). The model considers the following particles Nb6O198–, H3Nb6O195–, H4Nb12O368–, H6Nb12O366–, H10Nb12O362–, H12Nb12O36 and NbO2+. The concentration equilibrium constants obtained at different ionic strengths (from 0.001 to 0.008 M) were processed by Pitzer method to yield the values of the thermodynamic equilibrium constants of isopolyniobate anions formation from the NbO2+ cations. The distribution diagrams of isopolyniobate anions in aqueous solutions were plotted which allowed establishing the fields of dominant anions as a function of the solution acidity. The standard Gibbs energies of isopolyniobate anions formation were calculated. These data allow estimating the thermodynamic probability of reactions which can be used in the synthesis of salts containing the anions under consideration. A scheme of isopolyniobate anions behavior in aqueous solution was proposed which included isopolyniobate anions both of the 6th row and of the 12th one with the different number of protons. It was shown that the particles of the 12th row with an even number of protons are formed from the particles with also even but less content of H+ whereas the particles with the odd number of protons are formed from the particles with odd content that is by two parallel-flowing streams, respectively.

53-60

Authors: M.V. Ved, N.D. Sakhnenko, A.V. Karakurkchi, I.Yu. Yermolenko

The features of Fe-Mo and Fe-Mo-W coatings electrodeposition from a citrate bath containing iron (III) on mild steel and cast iron substrates are investigated in the present work. The application of iron (III) compounds significantly enhanced the stability and service life of the bath due to elimination of redox reactions involving complexes formation and collateral anodic reactions. The effect of the content of alloying components and electrolysis mode on the quality, composition and properties of the alloys are determined. It is shown that alloys formed under a non-stationary electrolysis condition have uniform surface and composition and contain fewer impurities. Improved physical and mechanical properties as well as higher corrosion resistance of Fe-Mo and Fe-Mo-W coatings compared with the basic metal are caused both by the propensity of alloying components for passivation and by an amorphous structure of electroplated alloys. The coatings under study are considered as promising in surface hardening technologies and for repairing worn items.

66-69

Authors: I.L. Kovalenko

An interaction of ammonium nitrate and binary systems "ammonium nitrate/sodium nitrate" and "ammonium nitrate/calcium nitrate" with powdered natural pyrite is considered in the present paper. The presence of calcium and sodium nitrate during the thermal decomposition of moistened systems was shown to reduce the total heat release 1.5-2.2 times; the rate of differential temperature is simultaneously rising 4-6.5 times, at the same time the temperature of the beginning of system exothermic decomposition falls 30 degrees. The influences of pH and the chemical nature of energy condensed emulsion systems sensitization on the reaction intensity with pyrite have been shown. It was established that the emulsions with pH 7.8-8.4, sensitized with solutions of hydrogen peroxide, have the lowest sensitivity to pyrite. It is concluded that the chemical nature of the emulsion sensitizer is a main factor in producing of energy condensed emulsion systems for safe use in sulfide rocks.

76-82

Authors: L.A. Melnyk, Yu.V. Babak, A.J. Samsoni-Todorov, V.V. Goncharuk

The membrane desalination processes of the standard test solutions containing As(V) and As(III) compounds are investigated. The ion-exchange membranes MK-40, MA-40 and reverse osmotic membrane ESPA-1 have been used as membranes. It is shown that the method of electrodialysis does not allow receiving the dialysates satisfying the requirements to the content of this trace element (10 µg/L) in potable water even at a rather low As contents in water (from 50 to 100 µg/L). The retention coefficient of As(V) during reverse osmotic desalination reaches 97.7 to 99.0% at an initial concentration of arsenic in solution of 50 to 300 µg/L while the similar characteristic for As(III) reaches only 75.5%. Thus, the full transformation of As(III) to As(V) by pretreatment provides a highly effective removal of arsenic compounds during reverse osmotic treatment. It was shown that the application of preliminary ultraviolet (UV) or UV/TiO2 treatments of the As(III) containing solutions with a duration of 1 to 5 minutes provides an increase in the retention coefficient of arsenic by membrane ESPA-1 up to 97.1-98.0%, the concentration of this microcomponent in permeate being reduced to 0.8-2.9 µg/L.

87-89

Authors: O.V. Podoby, G.V. Sokolsky, S.V. Ivanov

An overview of the current state and origins of chemistry at National University of Food Technologies is made on the occasion of its 130th anniversary. The role of prominent chemists in the foundation and establishment of the University and its prestige in Ukraine and abroad are shown.