Free-radical addition of aliphatic carboxylic acids to dialkyldiallylsilanes

Summary When reaction is initiated with t-butyl peroxide, carboxylic acids add to one double bond of dialkyldially lsilanes with subsequent homolytic intramolecular cyclization of the intermediately formed free radical with formation of a compound containing a silicon atom in a six-membered ring.     

Nitroazines. 20. Simple syntheses of nitropyrazolopyridines from aliphatic nitrosynthons and aminopyrazoles

Two variants of a synthesis for nitropyrazolopyridines from aminopyrazoles and two- or three-carbon nitrosynthons are examined.For Communication 19 see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1560–1564, November, 1992.     

Isomerization of perfluorinated cyclic amines under the action of antimony pentafluoride

Conclusions When perfluorinated tertiary cyclic amines containing a substituent at the nitrogen atom are heated with antimony pentafluoride, they isomerize to the corresponding azomethines.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 646–649, March, 1989.     

Radiothermoluminescence of polycrystalline high-temperature superconducting YBa2Cu3O6.94, EuBa2Cu3O6.9, and SmBa2Cu3O6.9 samples

Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, p. 1934, August, 1991.     

Aqueous and nonaqueous lithium-air batteries enabled by water-stable lithium metal electrodes

The extremely high theoretical energy density of the lithium-oxygen couple makes it very attractive for next-generation battery development. However, there are a number of challenging technical hurdles that must be addressed for Li-Air batteries to become a commercial reality. In this article, we demonstrate how the invention of water-stable, solid electrolyte-protected lithium electrodes solves many of these issues and paves the way for the development of aqueous and nonaqueous Li-Air batteries with unprecedented energy densities. We also show data for fully packaged Li-Air cells that achieve more than 800 Wh/kg.     

Highly regioselective synthesis of trifluoromethyl derivatives of pyrazolo[1,5-a]pyrimidines bearing fused cycloalkane rings using (2-ethoxycycloalkenyl)-2,2,2-trifluoroethanones

8-Trifluoromethyl-6,7-dihydro-5H-1,4,8a-triaza-s-indacene and 9-trifluoromethyl-5,6,7,8-tetrahydropyrazolo[5,1-b]quinazolines were efficiently generated by condensation of 5(3)-aminopyrazoles with (2-ethoxycycloalkenyl)-2,2,2-trifluoroethanones and isolated in excellent yields. The regiochemistry of the prepared compounds was established by ¹H, ¹³C and ¹⁹F NMR spectroscopy and X-ray diffraction analysis.     

Conformational properties of <Emphasis Type="Italic">ortho</Emphasis>-nitrobenzenesulfonamide in gas and crystalline phases. Intra- and intermolecular hydrogen bond

A combined gas-phase electron diffraction and quantum chemical (B3LYP/6-311+G**, B3LYP/cc-pvtz, MP2/cc-pvtz) study of molecular structure of 2-nitrobenzenesulfonamide (2-NBSA) was carried out. Quantum chemical calculations showed that 2-NBSA has four conformers, two of which are stabilized by intramolecular hydrogen bond. The latter (with the S–N bond in a close to orthogonal position around the phenyl ring and differing from each other by staggered or eclipsed positions of the N–H and S=O bonds in the SO₂NH₂ group) presented in a saturated vapor over 2-NBSA at T = 433 (3) K in commensurable amounts. Experimental internuclear distances (Ǻ) for the staggered conformer are (?): r _h1(C–H)_av. = 1.071(9), r _h1(C–C)_av. = 1.390(4), r _h1(C–S) = 1.789(8), r _h1(S=O)_av. = 1.427(6), r _h1(S–N) = 1.644(6), r _h1(N–O)_av. = 1.221(4), r _h1(C′–N) = 1.487(8), r _h1(N–H)_av. = 1.014. Calculations at B3LYP/cc-pvtz level were performed to determine the structure and the energies of the transition states between conformers. It was shown that the conformer structures of free molecule differ from those of a molecule stabilized by intermolecular hydrogen bonds in a crystal. Influence of a substituent X (X = –CH₃, –NO₂) on conformational features of the ortho-substituted benzenesulfonamide was established.     

Study of regioselectivity of reactions between 3(5)-aminopyrazoles and 2-acetylcycloalkanones

Regioselectivity was examined of reactions between nine 3(5)-aminopyrazoles and 2-acetylcyclopentanone and 2-acetylcyclohexanone under various conditions. A series of cyclopenta[e]pyrazolo-[1,5-a]pyrimidines was obtained. The highest regioselectivity of the reaction was observed in alcohol at 20°C in the presence of a catalytic quantity of trifl uoroacetic acid. The regiostructure of compounds was established by ¹H and ¹³C NMR spectroscopy.     

Synthesis of porous zirconium and titanium dioxides by hydrolysis of tetrabutoxyzirconium (tetrabutoxytitanium) with atmospheric moisture in the absence of acid-base catalysts with the use of cellulose and activated charcoal as matrices

Synthesis of porous zirconium and titanium dioxides was accomplished by a procedure that includes impregnation of cellulose and activated charcoal matrices with tetrabutoxyzirconium (tetrabutoxytitanium) solutions, hydrolysis of the precursors with atmospheric moisture at 25°C, burning the matrix, and incineration of xerogels at 850°C. Relationship between precursor solution concentration at impregnation stage, matrix type, and physicochemical properties of prepared materials was established.     

Quantitative analysis of undefined mixtures - "fishing net" algorithm

An approach for quantitative analysis of mixtures with unknown individual responses of the components is discussed. Although it is based on a resolution of overlapping bands technique, the main emphasis is not given to the computational facets of curve fitting. A logical procedure is described, allowing estimation of the unknown concentrations in the mixture, and both the number of overlapping bands and their assignment to the components in the solution to be determined automatically. A general conclusion about the precision of the method cannot be defined, because it depends on the extent of overlapping of the individual spectra of the components and their complexity. Using this procedure a complicated three-component acid-base equilibrium of a halochromic dye in solution is studied.