Ukrainian Chemistry Journal

Contents of Volume 81 №10 (2015)

Inorganic and Physical Chemistry

Semiempirical calculation of the structure of the aliphatic beta-ketoesters tautomers
  • Summary: For the simplest aliphatic beta-ketoesters (methyl, ethyl, propyl and allyl acetoacetate) the calculations of isomeric structures and conformational and tautomeric transformations energies were performed by means of the semiempirical PM7 method. The co nformer with S-shape of the [OCCCO] moiety was found to have the lowest energy among the keto tautomers due to the minimal electrostatic repulsion between three oxygen atoms in the beta-ketoester molecule. The cis-isomer in which the enolization takes place at the oxygen atom of the carbonyl, but not the ester, CO-group is the most stable enol tautomer. The enol tautomers possess planar structure (point group CS) due to p-bonds delocalization and their stability is also caused by the presence of the intermolecular hydrogen bonding. The keto-enol equilibrium constants calculated (K=0.1–0.5) indicate the equilibrium to be slightly shifted towards the ketotautomer.
  • Keywords: beta-ketoesters, semiempirical calculations, PM7, conformational search, intermolecular hydrogen bonding, keto-enol equilibrium.
  • pp.: 73 - 80

Isostructural iridium selenogalogenides Ir2Se9Hal6 (Hal – Cl, Br)
  • Summary: Two isostructural complexes Ir2Se9–Hal6 (Hal – Cl, Br) were obtained in non-aqueous chalcohalides medium at 100 °C. X-ray powder diffraction data showed that these compounds can be considered as "nanocomposites" formed by a stabilization of neutral cyclic Se9 cluster by two IrHal3 molecules, which are the part of the two distorted Ir[Hal3Se3] octahedra. It has been found by Raman spectroscopy that the synthesized compounds contain such chemical bonds as Ir–Hal, Ir–Se, Se–Se. These selenohalides of iridium are isostructural to selenohalides of rhodium Rh2Se9Hal6 (Hal – Cl, Br). All these compounds form a family of Se9-containing chalcohalides complexes of platinum metals.
  • Keywords: chalcohalides, iridium, selenium, sulfur, chlorine, bromine, ring-crown, liquid media.
  • pp.: 81 - 86

Hydrothermal synthesis of nanocrystalline ZrxCe1–xO2 solid solutions
  • Summary: It has been shown that the hydrothermal conditions ensure the synthesis of nanostructured solid solutions ZrxCe1–xO2 (x = 0.1—0.6) of cubic system with fluorite structure using the decomposition products of domestic zircon concentrate and cerium (III) nitrate. Uniformly sized (2 nm) nanoparticles of ZrxCe1–xO2 solid solutions are formed at 180 oC. Increasing the temperature to 300 oC significantly reduces the synthesis duration, but the size of the synthesized particles in this case depends on the zirconia content of solid solution and is the lower, the greater this content. Calcium cations which are present in the initial solutions of decomposition products of zircon concentrate are incorporated in the crystal lattice of solid solutions and increase the unit cell parameters.
  • Keywords: hydrothermal conditions, zircon concentrate, solid solutions, nanoparticles, zirconia, calcium cations.
  • pp.: 87 - 91

Spectroscopic research of interactions in MgF2—MgO—Ge system
  • Summary: By spectroscopic methods interaction of oxygen-containing admixture (MgO) in MgF2 with elemental germanium accompanied by their removal in the form of GeO which occurs at T >800 oС is investigated. Similar reaction in MgO—Ge system results in formation of magnesium germanates which almost completely block the process of GeO evaporation. The possible reasons of distinctions of processes, and also ways of their practical use, in particular, for an estimation of the content of MgO admixture in MgF2 and its elimination are regarded.
  • Keywords: spectroscopy, elemental germanium, magnesium germanates.
  • pp.: 92 - 96

Comparative evaluation of the water purification from humic acids by adsorption and adagulation using layere silicates
  • Summary: Critically reviewed various options for the removal of humic acids (HA) from aqueous solutions. It is shown that the most effective method of water purification from HA is adagulation in the joint application of the coagulant and adsorbent.
  • Keywords: adsorption. coagulation, adagulation, kaolinite, humic acids.
  • pp.: 97 - 103


Physical and chemical effects of alkaline metal carbonates on the nature of stibnite’s conductivity
  • Summary: The research of electrical conductivity of the melts of Sb2S3—Me2CO3 systems, where Me – Li, Na, K, in all interval of composition at temperatures from tmp to 1000 оC was conducted. In such melts as Sb2S3—Na2CO3, which are the most promising for use in industrial processes, the proportion of ionic conductivity, antimony’s solubility and electrolysis were studied depending on composition and temperature. The transformation of the nature of the stibnite’s (Sb2S3) conduction under the influence of alkaline metal carbonates is explained from the standpoint of the phenomenological theory of multifunctional conductivity of chalcogenide systems. Replacement of an alkaline metal in carbonates by the heavier one leads to natural changes in the values of electrical conductivity and melting temperatures of samples of Sb2S3—Na2CO3 systems and almоst doesn’t affect the process of the interaction and transformation of the nature of the conduction Sb2S3 from ion-electron to ion.
  • Keywords: stibnite, alkali metal carbonates, nature of conductivity, solubility antimony, electrolysis.
  • pp.: 104 - 110

Application of chronopotentiometry with controlled alternating current for the investigation of electrochemical properties of p-benzoquinone and p-dihydroxybenzene
  • Summary: Electrochemical properties of the acidic aqueous solutions of the "p-benzoquinone—p-dihydroxybenzene" redox-system on the platinum microelectrode have been studied by the method of chronopotentiometry with controlled sinusoidal current. It was shown that the ultra-fast change of electrode polarization potential provides an opportunity more accuratemechanism of electrode process to observed. In particular, it enables to define the role of "oxygenous" region of potentials for solutions on the sulfate solution; the role of the chemically produced oxygen in the chloride solutions; the role of conjugated chemical transformations of p-benzoquinone.
  • Keywords: chronopotentiometry, "oxygenous" region of potentials, conjugated chemical transformations of p-benzoquinone.
  • pp.: 111 - 116

Organic Chemistry

Association constants of the carbenoid azolium salts in acetonitrile
  • Summary: The constants of interionic association were determined by conductometry method in acetonitrile for carbenoid salts, derivatives of imidazolium, benzimidazolium and their macrocyclic bisazolium analogues of crown and cyclophane structures that are used for the synthesis of carbene metal catalysts. The influence of the salt structure on association constants is considered. It was shown that the association constants increase notably from monoazolium salts to macrocyclic analogues and the influence of the salt structure on the association constants is somewhat smoothed.
  • Keywords: association constants, carbenoid imidazolium, benzimidazolium, crown-bisimidazolium, crown-bisbenzimidazolium salts, bisimidazolium cyclophanes.
  • pp.: 117 - 123

Combined effects of structure and temperature in reactions between phenyloxirane and N-aroylarenesulfonamides. Cross-correlation analysis
  • Summary: The kinetics of reactions between phenyloxirane and N-aroylarenesulfonamides YC6H4-CONHSO2C6H4Z in acetonitrile at different temperatures have been studied. It has been found using cross correlation analysis that the combined effects of structure (substituents Y, Z) and temperature on the rate of oxirane ring opening are additive. The mechanism of the investigated reactions is discussed.
  • Keywords: reactions phenyloxirane, cross correlation analysis, multiple-factor kinetic experiment.
  • pp.: 124 - 128





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