Reaction of cyanamides with N,N-binucleophiles

Reactions of 4,6-dimethylpyrimidin-2-yl-and aroylcyanamides with benzene-1,2-diamine, ethylenediamine, cyclohexane-1,2-diamine, and naphthalene-1,8-diamine leads to 1H-benzimidazol-2-amine, imidazolidin-2-imine, perhydrobenzimidazol-2-imine, and 1H-perimidin-2-amine derivatives, respectively.     

Quantum chemical simulation of the reaction of methane with gold(I) acetylacetonate and aquaacetylacetonate complexes

The interaction between methane and gold(I) acetylacetonate via electrophilic substitution (reaction (I)) and oxidative addition (reaction (II)) is simulated. In both cases, the formation of the products is thermodynamically favorable: the decrease in energy is 31 kcal/mol for reaction (I) and 26 kcal/mol for reaction (II). The product of reaction (II) is additionally stabilized by Au-H interaction. Both reactions have a low activation barrier and proceed via the formation of structurally different methane complexes reducing the energy of the system by 9.3 kcal/mol for reaction (I) and by 10.9 kcal/mol for reaction (II). The complex [Au(H₂O)(acac)] is also capable of forming methane complexes. These complexes result from a thermally neutral reaction and turn into products after overcoming a low energy barrier. The structure of the complex activating methane in the gold-rutin system is deduced from the data obtained.     

Dependence of the structure of the gas hydrate framework on the parameters of guest-host interactions for lennard-jones guests

The energies of formation of hydrates from ice Ih and gaseous guests for 7 cubic and hexagonal frameworks are compared. The ranges of the parameters of the guest-host interaction potential within which one of the structures possesses lower energy than the others are determined. Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 37, No. 5, pp. 916–922, September–October, 1996. Translated by L. Smolina     

Effect of the nature of the solvent and the temperature on the frequency and intensity of the stretching vibration of the Ge-H bond in the IR spectra of 1-hydrogermatranes

Conclusions The Ge-H stretching vibration in the IR spectra of 1-hydrogermatranes varies under the influence of the solvent and the temperature as a result of the presence of the transannular Ge N bond. The change in the length of this bond with variation in the polarity of the solvent and the temperature of the solutions is smaller in germatranes than for the Si N bond in the isostructural silatranes.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1758–1761, August, 1985.     

Substituted pyrazine-di-N-oxides as the mediators of catalytic oxidation of organic compounds

The mechanism of oxidation of 2,5-dimethyl-, 2,3,5,6-tetramethyl-, 2,3-dimethyl-5,6-cyclohexa, and 3-phenyl-5,6-cyclohexapyrazine-di-N-oxides is studied by cyclic voltammetry, quantum chemical simulations, and ESR electrolysis. The studies are carried out on electrodes of glassy carbon and Pt in 0.1 M LiClO₄ solutions in acetonitrile. ESR spectra of radical cations of substituted pyrazine-di-N-oxides are recorded. The effects of the temperature, oxygen, and the additions of water, pyridine, and acid on the shape of cyclic voltamograms and the intensity of ESR signals of pyrazine-di-N-oxides are studied. A quantum-chemical simulation of the reaction of pyrazine-di-N-oxide radical cations with acetonitrile is carried out. The oxidation of substituted pyrazine-di-N-oxides is described by the E₁C₁E₂C₂ mechanism, which includes the stage of the formation of a complex between the di-N-oxide radical cation and acetonitrile.     

Topology of subsolidus sections of phase diagrams of quaternary reciprocal systems without solid solutions

A problem of constructing subsolidus isobaric–isothermal sections of phase diagrams of quaternary reciprocal systems with constant-composition compounds and limited solid solutions was considered. Relations between the topological characteristics of such sections were derived. Their topological classification was proposed. An algorithm for constructing sections using the theory of finite graphs was developed. A problem of enumerating sections for diagrams with a given set of classification characteristics was solved.     

METHODS TO DETERMINE CRYSTAL LATTICE PARAMETERS OF OPAL-LIKE STRUCTURES

Journal of Structural Chemistry - Series of high-quality spherical poly(methyl methacrylate) particles with a polydispersity less than 5% are prepared by chain-growth emulsifier-free controlled...