Showing papers in "Russian Chemical Bulletin in 1992"

Synthesis, molecular structure, and magnetic properties of bis(3,6-di-tert-butyl-o-benzosemiquinone)nickel(II) and -copper(II)

Abstract: The title complexes of Ni and Cu with symmetrical 3,6-di-tert-butyl-o-benzosemiquinone are synthesized. Their EPR spectra and magnetic properties are investigated. The x-ray structure studies [Siemens R3/PC diffractometer, λ MoKα, ϑ/20-scanning in the rang 2 ≤ 2ϑ ≤ 54°, 2084 reflections withF > 4σ(F),R = 0.034,Rw = 0.039, monoclinic crystals,a = 9.982(2),b = 11.548(2),c = 12.145(2) A, β = 95.05(3)°,Z = 2,dcalc = 1.19 g/cm−3, space groupP2l/c) demonstrated that the complex is monomeric with square-planar coordination for the Ni with theo-semiquinone ligands. The Cu complex is isostructural with the Ni (a = 9.88,b = 11.60,c = 12.15 A, β = 95°]. The dependence of the magnetic moment of the Cu complex on temperature is consistent with the presence in it of two pathways for exchange interaction. These are antiferromagnetic ligand-ligandJ12 = −179 cm−1 and ferromagnetic metal-ligandJ13 = 100 cm−1 (mean-square deviation 2%). The Ni complex is diamagnetic over the whole studied temperature range despite the fact that it contains free-radicalo-semiquinone ligands. Such an effect involving electrons belonging to the free-radical ligands is observed for the first time in the magnetochemistry ofd8- andd9-transition-metal complexes. It is explained by incorporation of vacantpz- and/or occupieddxz- anddyz-orbitals of Ni in molecular orbitals containing the π-MO of the semiquinone ligands.

Calculation of the van der Waals volumes of organic molecules

Abstract: A new and more precise method is proposed for calculating van der Waals atomic and molecular volumes of organic compounds. The method provides for intersections of three or more spheres at one point of space. Such a possibility is essential for calculating the volumes of sterically overcrowded molecules and of molecules with intramolecular hydrogen bonds. A computer program for IBM PC/AT(XT) is developed. Depending on the atomic environment in the molecule, the average values of the volume increments for atoms C, N, O, H, F, Cl, and S are obtained using the data from the Cambridge Structural Database.

Gem-dinitro compounds in organic synthesis. 3. Syntheses of 4-nitro-1,2,3-triazoles from gem-dinitro compounds

Abstract: Several chemoselective syntheses have been developed for 4-nitro-1,2,3-triazoles from sodium azide and gem-dinitroethylenes prepared from readily available transformation products of dinitroacetic acid ester: N-(β,β-dinitroethyl)-N,N-dialkylamines, 2,2-dinitroethanol acetate, a mixture of dinitroacetic acid ester with aliphatic aldehydes, or 1,1,1-trinitroalkanes. Hitherto-unknown 4-nitro-5-amino- and 4,5-dinitro-1,2,3-triazoles have been synthesized via successive transformations of the CH3 groups in 5-nitro-4-methyltriazole. Nitration of 4-nitro-1,2,3-triazole with nitronium fluoroborate or acetyl nitrate gave an unknown 2,4-dinitro-1,2,3-triazole.

Summary of development of the theory of stability of colloids and thin films

Abstract: In this review, the research of the author in the field of colloidal systems is summarized. The factors influencing colloidal stability are systematized and analyzed. Examples are presented to illustrate the practical utilization of the theory of stability of colloids and thin films.

Phosphorus-containing podands. 9. Synthesis of oligoethylene glycol bis(diphenylphosphinylethyl) esters and their complexing properties with respect to alkali metal cations in a low-polarity solvent

Abstract: The complexing ability of phosphoryl-containing monopodands with the general formula Ph2P(O)CH2CH2O(CH2CH2O)nCH2CH2P(O)Ph2 (n=0–5, 64, 87, 132) with respect to alkali metal cations was investigated conductometrically in tetrahydrofuran:chloroform mixed solvent (4:1, vol) at 25°C It was found that ligands of this type are efficient complexing agents relative to all alkali metal cations, and the monopodand with n=0 also exhibits elevated Li/Na and Li/K selectivity The effect of the structure, particularly the "rigidity" of the terminal fragments of the monopodands, on their complexing capacity was discussed The method of synthesis of this type of ligand was described

Synthesis of liquid crystal ferrocene derivatives and their complexes with Cu2

Abstract: A series of liquid crystal ferrocene-containing Schiff bases of general formula C5H5FeC5H4-C6H4-N=CN-(X)C6H3-O(O)-C6H4-OCnH2n+1 (X=H, OH, n=3–12) was obtained, together with several analogs, 1,1′-bis-substituted at the ferrocene fragment, having a thermotropic nematic mesophases. Derivatives with X=OH were used to obtain Cu2+ chelate complexes, of which the compounds with n=10 and n=12 displayed nematic liquid crystalline properties.

Photochemical oxidation of hydrocarbons by a vanadium(V) peroxo complex

Abstract: The oxidation of alkanes and benzene by VO(O2)L·2H2O (L=2-picolinate) in acetonitrile is accelerated upon irradiation with visible and, especially, UV light. Cyclohexyl hydroperoxide, cyclohexanol, and cyclohexanone in approximately 2:1:1 ratio are formed from cyclohexane both in the dark and photochemical reactions. Benzene is oxidized to phenol.

Investigation of the role of the pyrimidine ring in the main chain of polyamido acids and polyimides. 1. Supermolecular structure of polypyromellitimides based on 2,5-bis(p-aminophenyl)pyrimidine and its carbocyclic analog 4,4′-diaminoterphenyl

Abstract: A detailed comparative study of polypyromellitamido acids and polyimides based on 2,5-bis(paminophenyl)pyrimidine and 4,4′-diaminoterphenyl was conducted to determine the role of the nitrogencontaining pyrimidine ring in the main chain of the polymers. A model of the layer packing of polyimide chains in crystalline regions was proposed based on the data from x-ray structural analysis and quantum chemical calculations. The existence of tilted packing caused by partial displacement of the solvent molecules bound to the pyrimidine ring of the neighboring macromolecule with higher basicity in pyrimidine-containing polymers was hypothesized.

Rearrangement of the carbon skeletion of perfluorinated 1-isopropyl-, 1-methyl-1-isopropyl-, and 1-methyl-2-isopropylbenzocyclobutenes by the action of antimony pentafluoride

Abstract: Perfluorinated 1-isopropyl-, 1-methyl-1-isopropyl-, and 1-methyl-2-isopropylbenzocyclobutenes isomerize under the influence of antimony pentafluoride to perfluorinated alkylstyrenes and alkylindans. The process may be accompanied by dealkylation and also by fluorination and defluorination of the products. With antimony pentafluoride at 50°C perfluoro-1-methyl-1-isopropylbenzocyclobutene gives perfluoro-α,β,β,o-tetramethylstyrene, which isomerizes under the influence of antimony pentafluoride at 130°C into perfluoro-1,2,2-trimethylindan, and the latter forms perfluoro-2,3-dimethylindene under the reaction conditions. Perfluoro-1-methyl-2-isopropylbenzocyclobutene is not changed in the presence of antimony pentafluoride at 50°C but isomerizes to perfluoro-1-isopropylindan at 90°C. The latter is transformed under these conditions into the above-mentioned tetramethylstyrene. Perfluoro-1-isopropylbenzocyclobutene does not react with antimony pentafluoride at 130°C, but at 170°C it gives a mixture of perfluorinated 2,2-dimethylindan, 2,3-dimethylindene, 2,3-dimethyl-4,5,6,7-tetrahydroindene, and 2-isobutyltoluene, which is converted into perfluoro-o-xylene under the reaction conditions.

An efficient dehydrofluorinating system for polyvinylidene fluoride

Abstract: Chemical dehydrohalogenation of halogen-containing polymers is an accessible and convenient method for preparation of carbon-chain polymers with a system of conjugated multiple bonds in the main chain, including carbyne [1]. The development of an efficient method of preparation of carbyne and articles made of it is still an urgent problem. It was previously shown that chemical dehydrohalogenation of polyvinylidene halides (PVDH) with an alcohol solution of a base causes the formation of a cumulene modification of carbyne [2]:

Catalytic synthesis and reactions of magnesiocycloalkanes. 2.* synthesis of substituted magnesiocyclopentanes in the presence of zirconium complexes

Abstract: Catalytic cyclometallation of styrene,m-methylstyrene,p-tert-butylstyrene, and 1-hexene with di-n-alkylmagnesium compounds (n-R 2 Mg, where R=C 3 H 7 , C 4 H 9 , and C 6 H 13 ) in the presence of Cp 2 Zr 2 Cl 2 has given high yields of 2,4-disubstituted magnesiocyclopentanes. The probable mode of formation of magnesiocyclopentanes, involving zirconocyclopentanes formed from Cp 2 ZrCl 2 ,n-R 2 Mg, and the appropriate olefins as reactive intermediates in the cyclometallation, is discussed.

Gem-dinitro compounds in organic synthesis. 4. Use of the condensation product of glyoxal and dinitromethane in the synthesis of nitro-1,2,3-triazoles

Abstract: The condensation of dinitromethane with glyoxal has been investigated and it has been demonstrated that 1,1,4,4-tetranitro-2,3-butandiol, α-hydroxy-β,β-dinitropropionic acid or their mixture may be formed. Interaction of 1,1,4,4-tetranitro-2,3-butandiol or 1,4-dibromo-1,1,4,4-tetranitro-2,3-butanediol diacetates with sodium azide leads to bis(5-nitro-1,2,3-triazol-4-yl) via intermediate 1,1,4,4-tetranitro-1,3-butadiene.

Boron chelates with 5,5,5-trifluoro- and 5,5,5-trichloro-4-aminopent-3-en-2-ones

Abstract: Boron chelates were obtained by the reaction of butoxy(butylthio)diphenylborane with 5,5,5-trifluoro(trichloro)-4-aminopent-3-en-2-one, and their reactions with primary amines were investigated. β-Diiminate complexes of boron with trifluoro- and trichloromethyl groups were synthesized.

Synthesis of shikalkin and certain related compounds

Abstract: A successful total synthesis of a biologically active pigment from plants of the Boraginaceae family was carried out with naphthazarine as the starting material, and using the 1,4,5,8-tetramethoxynaphthalene, the corresponding 2-vinyl derivative and its epoxide or a cyclopropane adduct with diazoacetic ester at the key stages. In the course of developing the scheme of the synthesis of shikalkin, its three analogs were obtained, differing in the nature of the monoterpenoid side chain.

13C NMR spectroscopy of tautomeric conversions in imidazole compounds

Abstract: A study has been made of13C NMR spectra of several series of imidazoles and their salts in solution and in the solid state. It has been shown that in compounds containing a pyridine ring, prototropic tautomerism on the NMR time scale may be retarded. The possible mechanism of these processes is discussed.

Synthesis of hydrogels from a polymeric N,N′-diallyl-N,N′-dimethylammonium salt

Abstract: Feasibility in principle has been demonstrated for obtaining hydrogels with controlled parameters of the three-dimensional network by copolymerization of N,N′-methylenebisacrylamine with macromolecules of poly-N,N′-diallyl-N,N′-dimethylammonium chloride containing terminal double bonds, i.e., with macromonomers of N,N′-diallyl-N,N′-dimethylammonium chloride. The hydrogels that are obtained have high anion-exchange capacities.

Synthesis and conversions of metallocycles. 8.13C NMR spectra of aluminocyclopentanes

Abstract: Using13C NMR spectroscopy we have studied disubstituted and trisubstituted aluminocyclopentanes, determined the spectral parameters, and made stereochemical assignments of the isomers. The structure of the studied organoaluminum compounds has been confirmed by analysis of the products of hydrolysis, deuterolysis, and oxidation of aluminocyclopentanes.

Mechanism of the gas-phase oxidation of carbon disulfide at elevated temperatures (the C-S-O system)

Abstract: Machine modeling was used to investigate the kinetic mechanism of the gas-phase oxidation of carbon disulfide at elevated temperatures The scheme of the process examined includes 70 elementary reactions On the basis of the kinetic data on these reactions available in the literature the rates of the oxidation process, the concentrations of end products and intermediate particles were calculated as a function of the time under various conditions (composition, pressure, temperature) Comparison of the results obtained with the experimental data showed satisfactory agreement and also revealed some important elementary reactions

Geometry and electronic structure of the dimethyl sulfoxide dimer. Calculation by the MNDO method

Abstract: The geometric and electronic structure of the complex formed by dipole-dipole interaction between two molecules of DMSO in the "head-to-tail" orientation were calculated by the MNDO quantum-chemical method. The minimum total energy corresponds to a distance of 5.5 A between the sulfur atoms, and the angle between the axis of the molecular dipoles is 16.4°. This agrees with calculations for liquid DMSO by molecular dynamics. The large equilibrium distance between the DMSO molecules explains its low density in the liquid phase and the high intensity of microwave absorption due to free volume sufficient for rotation of one molecule in the complex in relation to the dipole axis of the other.

Structural conversions of rhodamines in solution

Abstract: A study has been made of the acidic ionization, structural conversions, and prototropic tautomerism of rhodamine chromogens in methanol and dimethyl sulfoxide, using IR,13C NMR, and electronic spectroscopy. The lactone structure has been established for the colorless form of rhodamines in DMSO. For rhodamine B in mixtures of water with DMSO, the lactone/zwitterion ratio has been estimated.

Synthesis of 1-(2,4,6-trichlorophenyl)-2-(1,2,4-triazol-4-yl)-diazene-1-oxide

Abstract: By reaction of 4-amino-1,2,4-triazole with 1-nitroso-2,4,6-trichlorobenzene in the presence of excess dibromoisocyanurate the title compound was obtained.

Reaction of 2-methyl-4,5-dihydrofuran with hydrogen chloride

Abstract: Reaction of 2-methyl-4,5-dihydrofuran with HCl at 0°C yields 5′-chloro-2′-pentanone (13%) and 1′-(2-methyltetrahydrofuryl-2)-5′-chloro-2′-pentanone (27%) and at 200° 5′-chloro-2′-pentanone exclusively.

Reaction of 1,2-borylphosphinoethene with thiocyanates. Molecular and crystal structure of 2,2,3-tributyl-4,5,5-triphenyl-6-methylthio-1,5,2-azaphosphoniaboratacyclohexa-3,6-diene

Abstract: The reaction of 1,2-borylphosphinoethenes with alkylthiocyanates leads to formation of substances having the structure of 6-alkylthio-1,5,2-azaphosphoniaboratacyclohexa-3,6-dienes in the crystal state. The structure of the compounds has been proven by x-ray diffraction analysis of 2,2,3-tributyl-4,4,5-triphenyl-5-methylthio-1,5,2-azaphosphoniaboratacyclohexa-3,6-diene. The heterocyclic moiety of the molecule is planar within 0.010(2) A. The methylthio group lies practically in the plane of the heterocycle.

Reaction of silylated aminonitrofurazane with N-magnesium amine derivatives

Abstract: A study was carried out on the reaction of N-trimethylsilylaminonitrofurazane with magnesyl amines, leading to the corresponding asymmetric diazene oxides.

Synthesis of functional derivatives of 2-methylenecyclopentane and 2-methylenecyclohexane based on the allylborylation of imines, nitriles, isocyanates, and isothiocyanates by cycloalkenylmethyl(dipropyl)boranes

Abstract: A study has been made of the allylborylation of imines, nitriles, isocyanates, and isothiocyanates by the action of cycloalkenylmethyl(dipropyl)boranes. Preparative methods have been developed for obtaining amines, phenylamides, and phenylthioamides of the 2-methylenecyclopentane and 2-methylenecyclohexane series.

Reactions of highly electrophilic polyfluoro unsaturated compounds with pyrazole derivatives

Abstract: Pyrazole derivatives were hydroxyalkylated at the C4 atom by hexafluoroacetate and methyl trifluoropyruvate. The products of the hydroxyalkylation were dehydrated to the corresponding alkylidene derivatives which were reacted with nucleophiles. Dicyanoethylenes, obtained from polyfluorocarbonyl compounds, alkylated pyrazol-5-ones with the formation of pyrazolopyran derivatives.