Synthesis and crystal structure of 4-acetoxy-5,6-dihydro-5,5-dinitro-2H-1,3-oxazineN-oxide

A novel heterocyclic compound, 4-acetoxy-5,6-dihydro-5,5-dinitro-2H-1,3-oxazineN-oxide, has been synthesized by the reaction of the dipotassium salt of 1,1,5,5-tetranitro-3-oxapentane with aqueous acetic acid. The synthesized compound has been studied by X-ray diffraction analysis.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2207–2210, December, 1994.We would like to thank G. V. Lagodzinskaya (Institute of Chemical Physics in Chernogolovka, Russian Academy of Sciences) for recording and interpreting¹H NMR spectra, A. M. Korolev (Institute of Chemical Physics in Chernogolovka, Russian Academy of Sciences) for helpful discussion, and V. I. Fetisov (Institute of Physiologically Active Compounds, Russian Academy of Sciences) for performing quantum-chemical calculations by the AM1 SCF MO LCAO method.     

Spectroscopic Study of Reaction of Propargyl Bromide with Pyridine

Pyridine was reacted with propargyl bromide to obtain the dibromide [C₅H₅NCH = CHCH = CHCH = CHC₅H₅N]^{2 +} 2Br^-. The effect of the vinyl group on its UV spectrum is qualitatively interpreted using the results of nonempirical quantum-chemical calculations (basis HF/6-31G^*).     

Thermal oxidative degradation of a composition based on a polyester resin and tetramethylammonium chloride

Thermal oxidative degradation of a composition based on a polyester resin modified with rosin and tetramethylammonium chloride and its use as a flux for low-temperature solder pastes were studied.     

Problem of the extremal decomposition of a closed plane

One considers the problem of the maximum of the product of powers of conformal radii of nonoverlapping domains in the following formulation. Let A=a₁, ..., a_n and B=(b₁, ..., b_m be systems of distinguished points in ¯C and let ={₁,..., _m} be a system of positive numbers. ByU(D,b ) we denote the reduced modulus of the simply connected domain D relative to the pointb D. Find the maximum of the sum in the familyD of all systems of nonoverlapping simply connected domains D_j, j=1, ..., m, satisfying the following condition: the domain D_j does not contain points b_i B, different from b_j, and some collection A_j, for each domain, of points from A, _j=1 ^m A _j =A. The solution of this problem is obtained by the simultaneous use of the method of variation and of the method of the moduli of families of curves and is given by Theorem 1 of the present paper. As consequences of Theorem 1 one obtains Theorems 2 and 3, strengthening the corresponding results of a previous paper of the author.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova AN SSSR, Vol. 144, pp. 149–154, 1985.     

Solution conformation of a nitrobenzoxadiazole derivative of the polyene antibiotic nystatin: a FRET study

Nystatin is a polyene antibiotic frequently applied in the treatment of topical fungal infections. In this work, a 7-nitrobenz-2-oxa-1,3-diazole (NBD) hexanoyl amide derivative of nystatin was synthesized and its detailed photophysical characterization is presented. The average conformation of the labelled antibiotic in tetrahydrofuran, ethanol and methanol was determined by intramolecular (tetraene to NBD) fluorescence resonance energy transfer measurements. At variance with the literature [Can. J. Chem. 63 (1985) 77-85], it was concluded that there is no need to invoke a solvent-dependent conformational equilibrium between extended and closed conformers of the antibiotic, because the mean tetraene-to-NBD separating distance was found to remain constant (approximately 18 A) in all the solvents studied. In addition, the large solvent dependence of the fluorescence anisotropy observed for the non-derivatized nystatin, was rationalized on the basis of the prolate ellipsoidal geometry of the molecule. It was concluded that the rod shaped and amphipathic antibiotic remains monomeric in different solvents within the concentration range studied (2-20 microM).     

Interaction in the ternary system HgBr<Subscript>2</Subscript>-PbBr<Subscript>2</Subscript>-CsBr

Several vertical sections are investigated in the HgBr₂-PbBr₂-CsBr system by the methods of physicochemical analysis. Six compounds, namely, CsHg₂Br₅, CsHgBr₃, Cs₂HgBr₄, CsPb₂Br₅, CsPbBr₃, and Cs₄PbBr₆, are formed in the bordering binaries of the ternary system. By the results of investigation, the projection of the liquidus surface of the HgBr₂-PbBr₂-CsBr system on the composition triangle is constructed, and the fields of primary crystallization of nine phases are plotted, namely, HgBr₂, PbBr₂, CsBr, CsHg₂Br₅, CsHgBr₃, Cs₂HgBr₄, CsPb₂Br₅, CsPbBr₃, and Cs₄PbBr₆. An immiscibility region is found in the system. This region occupies a considerable part of the primary crystallization field of PbBr₂. The coordinates of invariant points are determined, and isotherms are plotted.     

Synthesis and investigation of the electronic structure of molybdenum tetrasulfide and its lithium intercalates

An X-ray amorphous phase of molybdenum tetrasulfide with the analytical formula MoS₄ has been sythesized. Quantum chemical modeling of the suggested local structure of MoS₄ and EHT calculation of the electronic structure of the basic (Mo₂S₄)⁴⁺ fragment are reported. The electronic structure of molybdenum tetrasulfide and its lithium intercalates was investigated by X-ray emission and X-ray photoelectron spectroscopy. It is shown that the change in the electronic structure of the starting molybdenum tetrasulfide to four lithium atoms per formula unit in the intercalate may be considered in the rigid band model. Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 37, No. 4, pp. 727–734, July–August, 1996. Translated by L. Smolina