Effect of the iron content on the properties of a zirconium dioxide catalyst in the hydrogenation of carbon monoxide

The hydrogenation of Co on zirconium dioxide catalysts containing from 0 to 10 mass % iron was studied. Small additions of iron up to about 0.5 mass % promote the ZrO₂ catalysts relative to the formation of C₂–C₄ olefins. In the presence of large iron additives, the catalyst operates as a complex metal-oxide system featuring interaction of its components. L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 Prospekt Nauki, 252039 Kiev, Ukraine. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 33, No. 3, pp. 153–158, May–June, 1997.     

Nonlinear Brönsted relationships and the α-effect of oximate ions in acyl* transfer reactions

A detailed extrathermodynamic analysis of the behavior of oximate ions (pK_a≈7–13) in reactions with various types of substrate was undertaken. For oximate ions with pK_a≥9.0, irrespective of the nature of the acyl group, the reactivity of the oximes tends toward that of the alcoholate ions, and their α-effect disappears. The reason for this is the unfavorable solvation effects of the solvent. Institute of Physical Organic Chemistry and Coal Chemistry, National Academy of Sciences of Ukraine, 70 R. Lyuksemburg ul., Donetsk 340114, Ukraine. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 34, No. 2, pp. 86–90, March–April, 1998.     

Role of dimethylformamide in generating the active form of platinum for catalyzing the synthesis of diaryls from aryl iodides

A mechanism is proposed for the reaction of aryl iodides with platinum(II) tetrachloride complexes in dimethylformamide including formation of PtCl₃(CONMe₂)²⁻ in the first step through activation of a dimethylformamide C−H bond by platinum(II) and subsequent oxidative addition of ArI to this species. L. M. Litvinenko Institute of Physical Organic and Coal Chemistry, National Academy of Sciences of Ukraine, 70 Lyuksemburg ul., Donetsk 340114, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 34, No. 4, pp. 244–246, July–August, 1998.     

Electrochemical oxidation of sulfodifluoroacetic acid in the presence of halogens

The electrochemical oxidation of sulfodifluoroacetic acid (HOSO₂CF₂CO₂H) in the presence of Cl₂ or Br₂ gives halodifluoromethanesulfonic acid. The anodic oxidation of sulfodifluoromethanecarboxylate ion to form the sulfodifluoromethyl radical as an intermediate is proposed as the rate-determining step. Institute of Organic Chemistry, National Academy of Sciences of Ukraine, 5 Murmanskaya ul., Kiev 253094, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 35, No. 4, pp. 246–248, July–August, 1999.     

Active intermediates in the oxidative bromochlorination of olefins in concentrated hydrochloric acid

A study was carried out on the oxidative bromochlorination of olefins in the presence of KBr using hydrogen peroxide and an electrochemical technique. Asymmetric trihalide anions, Br₂Cl⁻ and BrCl₂ ⁻, were found to be the active bromochlorination reagents. The reaction mechanism was discussed. Institute of Organic Chemistry, National Academy of Sciences of Ukraine, 5 Murmanskaya St., 253660 Kiev-94. Ukraine. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 33, No. 4, pp. 248–251, July–August, 1997.     

Separation of C1–C4 hydrocarbon gases on impregnated liquid membranes

Diffusion plays an important role along with complexation in the separation of C₁–C₄ hydrocarbon gases on copper-containing impregnated liquid membranes. The partition factor changes as the process goes from nonsteady-state to steady-state. L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 Prospekt Nauki, Kiev 252039, Ukraine. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 34, No. 3, pp. 191–195, May–June, 1998.     

Peculiarities of the mechanism of chlorotropic and conformational isomerism in a series of chloromethyl isocyanates

The thermodynamic and kinetic stability of chlorotropic isomers in a series of chloromethyl isocyanates Cl_3−nH_nC−N=C=O, where n=0, 1, 2, has been shown by quantum chemical calculations, using the MNDO method, and by³⁵Cl NQR spectroscopy. The phase transformations of two polymorphic modifications of N-chlorocarbonyl dichloride, which is a stable iminocarbonyl form of trichloromethyl isocyanate with small conformational activation barriers, have been studied. Institute of Bioorganic and Petrochemistry, National Academy of Sciences of Ukraine, 1 Murmansk ul., Kiev-94 252660, Ukraine. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 34, No. 3, pp. 164–169, May–June, 1998.     

Dehydrocondensation of methane to higher hydrocarbons on bifunctional catalysts in the absence of oxidizing agents in the gas phase

A study was carried out on the effect of the chemical nature of M_xL_y on the activity and selectivity of bifunctional M_xL_y/zeolite catalysts, where M_xL_y are metal-like transition metal compounds, M is a metal atom (Co, Mo, or W), and L is a nonmetal atom (B or Si), in the dehydrocondensation of methane to give higher hydrocarbons in the absence of gas-phase oxidizing agents. L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 Prospekt Nauki, 252039 Kiev, Ukraine. Translated from éksperimental’naya i Teoreticheskaya Khimiya, Vol. 33, pp. 243–247, July–August, 1997.     

Compounds of the [PMo12O40]3− anion with surfactant cations forming nanoperiodic structures

Phosphomolybdic acid forms compounds with surfactant cations in acid aqueous media (pH 1.0–2.5) to give compounds A₃[PMo₁₂O₄₀] or Etn₃[PMo₁₂O₄₀]₂·nEtnCl₂ (n=0−3) with various nanoperiodicity depending on the surfactant and synthesis conditions. L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 Prospekt Nauki, Kiev 252039, Ukraine. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 34, No. 3, 184–190, May–June, 1998.     

Modeling of the kinetics of the heterogeneous-homogeneous conversion of methane into ethane and ethylene in the absence of oxygen in the gas phase

Computer calculations were carried out on the kinetics of the gas phase chain process for the conversion of methyl radicals into higher hydrocarbons in an oxygen-free atmosphere based on a scheme of reactions consisting of 23 homogeneous elementary steps and the heterogeneous stage of methyl radical formation. The results of the calculations are in good agreement with experimental kinetic results obtained for the interaction of methane with the oxidized surface of the perovskite catalyst KNaSrCoO₃. L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 Prospekt Nauki, Kiev 03039, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 36, No. 4, pp. 222–225, July–August, 2000.     

Effect of the nature of the support on the activity of palladium catalysts for oxidation of carbon monoxide

We have studied the catalytic activity of TiN_0.65, TiO₂, Al₂O₃, and palladium catalysts supported on them in the oxidation of carbon monoxide. The order in which the activities of the supported catalysts vary, Pd/Al₂O₃>Pd/TiO₂>Pd/TiN_0.65, is the reverse of the activity series for the supports. This is explained by the effect of transfer of electron density from the palladium to the substrate. Taras Shevchenko Kiev University, 64 Vladimirskaya ul., Kiev 252033, Ukraine, G. V. Kurdyumov Institute of the Physics of Metals, National Academy of Sciences of Ukraine, 36 Akademika Vernadskogo bul’var, Kiev-142 252642, Ukraine. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 34, No. 2, pp. 118–121, March–April, 1998.     

The effect of encapsulated cyanide complexes on the localization of cations in faujasite

Features of the localization of various types of cations and their distribution between the structural elements of the framework of faujasite with encapsulated hexacyanide complexes of iron(II) and cobalt(III) were established. The content of the alkali-metal cations in the sodalite cells is increased compared with faujasite, and the cations of the transition metals are localized in the large cavities with the formation of Me(S_II)−NC−Fe(CN)₅ (Me=Cu, Co) and (NC)₅Fe−CN−Me(S_V)−NC−Fe(CN)₅ (Me=Ni, Cu, Co) fragments. L. V. Pisarzhevskii Institute of Physical Chemsitry, National Academy of Sciences of Ukraine, 31 Prospekt Nauki, Kiev 252039, Ukraine. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 35, No. 1, pp. 56–61, January–February, 1999.     

The effect of the modification conditions of natural mordenite on their catalytic characteristics in the selective reduction of NOx

The results of a search for optimum conditions for the modification of natural mordenites and the results of an investigation of their acidic characteristics by temperature programmed desorption of ammonia for the purpose of producing active and sulfur-resistant catalysts for the selective reduction of NO_x by lower hydrocarbons (C₁−C₄) are presented. It was shown that during the chemical modification of samples of mordenite-bearing rock, including acid treatment with 0.25–0.5 N sulfuric acid solutions, recationization, and subsequent decationization, the concentration of strong acid centers increases. Here the activity of the catalysts and the resistance to the effect of SO₂ in the selective reduction of NO_x to nitrogen by a propane-butane mixture are increased. L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 Prospekt Nauki, Kiev 252039, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 35, No. 2, pp. 125–129, March–April, 1999.     

Geometric isotope effect in hydrogen-containing crystals of the KH2PO4 type

The geometric isotope effect in hydrogen-containing crystals of the KH₂PO₄ type has been investigated. A mechanism is proposed which leads to a change in the lengths of hydrogen bonds on replacing a proton with a deuteron. It is shown that, to obtain agreement between experimental and theoretical results within the limits of the three-dimensional model for describing the hydrogen bonds based on the Einstein approximation, it is necessary to take into account interactions between the chains of hydrogen bonds in the crystals. Institute of Physics, National Academy of Sciences of Ukraine, 46 Prospekt Nauki, Kiev 03650, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 36, No. 4, pp. 213–217, July–August, 2000.     

Stereochemical features of the synthesis and the structure of fullerenes

Details of the design of decaplet fullerenes are discussed. A model of the cluster assembly of C₆₀, C₇₀, and C₈₀ monomers from mono-, bi-, and trihexacyclic compounds of carbon was developed on the basis of the described structural and stereochemical concepts. The autoadhesion in the supermolecular structure, the cluster macrorecombination of the π radicals, and the contribution from spin-polymerization effects to regulation of the organic synthesis of C_n fullerenes were examined. V. N. Bakul Institute of Superhard Materials, National Academy of Sciences of Ukraine, 2 Avtozavodskaya ul., Kiev 254074, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 35, No. 3, pp. 145–149, May–June, 1999.     

Kinetics of nonstationary condensation of methane on a perovskite catalyst

The interaction of methane with the oxidized surface of the KNaSrCoO_3−x is first order in methane with respect to formation of higher hydrocarbons and zero order with respect to formation of CO₂. At the initial stage the rate of formation of the reaction products is independent of the amount of oxygen from the catalyst consumed (up to 5–7 monolayers of oxygen), after which the rate of the reaction falls linearly. The overall amount of oxygen consumed in the reaction reaches 30 monolayers. L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 Prospekt Nauki, Kiev 03039, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 36, No. 3, pp. 182–187, May–June, 2000.     

Rate constants for the formation and decomposition of the σ-adduct in the reactions of N-arylpyridinium salts

The rate constants for the formation (k₁) and decomposition (k ₋₁ ,k ₂ ,k ₃ ) of the σ-adduct were determined for the reactions of 4-R-N-(2,4-dinitrophenyl)pyridinium salts [R=Py, CON(C₂H₅)₂] with 4-methoxyaniline, which takes place by the ANRORC substitution mechanism. L. M. Litvinenko Institute of Physical Organic Chemistry and Coal Chemistry, National Academy of Sciences of Ukraine, 70 R. Lyuksemburg ul., Donetsk 340114, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 34, No. 5, pp. 282–285, September–October, 1998.     

Temperature dependence of the substrate selectivity in the hydroxylation of alkylbenzenes in the H2O2−H2SO4 system

The substrate selectivity in the hydroxylation of methylbenzenes in the H₂O₂−H₂SO₄ (70 wt.%) system was studied at 15–55 °C. The activation entropy correlates with the basicity of the arenes, while the substrate selectivity and activation enthalpy correspond both with the basicity and ionization potentials of ArH. We concluded that the structure of the reaction transition state is intermediate between a charge transfer complex and σ-complex. L. M. Litvinenko Institute of Physical Organic and Coal Chemistry, National Academy of Sciences of Ukraine, 70 R. Lyuksemburg ul., Donetsk 340114, Ukraine. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 35, No. 1, pp. 39–43, January–February, 1999.     

Nature and degree of distortion of TiO2 (Anatase) surface octahedra upon formation of Ti3+ ions

We show that in the transition from Ti(IV) to Ti(III), on the surface of anatase the TiO_6/3 octahedra undergo compressive tetragonal distortion. The axial Ti−O bond length in the octahedron decreases in this case by at least 0.0027 nm. Institute of Surface Chemistry, National Academy of Sciences of Ukraine, 31 Prospekt Nauki, Kiev 252022, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 35, No. 4, pp. 253–256, July–August, 1999.     

Kinetics and mechanism of the oxidation of arenes in the presence of heteropoly acids and palladium(II) complexes supported on silica gel

Pd(II) complexes and twelfth-series heteropoly acids (HPA) H₉[PMo₆V₆O₄₀] and H₃[PMo₁₂O₄₀] supported on silica gel oxidize benzene and toluene at 95°C. The formation of methyldiphenylmethane in the oxidation of toluene on HPA/SiO₂ and (PdCl₂−HPA)/SiO₂ catalysts, KIE>1 for the toluene/toluene-d₈ pair, and greater rate for toluene than for benzene are in accord with a one-electron transfer mechanism. L. M. Litvinenko Institute of Physical Organic and Coal Chemistry, National Academy of Sciences of Ukraine, 70 R. Lyuksemburg ul., Donetsk 340114, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 35, No. 4, pp. 249–252, July–August, 1999.