Tetrazoles. 20. Tetrazolium salts in interphase catalysis

Oxidation of substituted triaylformazanes by potassium permanganate in a twophase organic solvent-water system in the presence of catalytic amounts of tetrabutylammonium bromide gives the corresponding tetrazolium salts, which are interphase transfer catalysts in oxidation, alkylation, and esterification. From distribution coefficient data it is concluded that 2,3,5-triphenyltetrazolium chloride has less catalytic activity than 2,5-diphenyl-3-(m-nitrophenyl)-tetrazolium bromide.Communication 19, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 841–845, June, 1985.     

Untersuchungen zum System Te/O/I

Investigations on the System Te/O/I By DTA measurements and by total pressure measurements was derived, that only a small solubility exists for TeI₄ in TeO₂, a composition of the typ Te₆O₁₁X₂ does not exist. The existenz of TeOI₂ in gas phase was derived from the transport behaviour of TeO₂ with I₂ and TeI₄ respectively. The enthalpy of formation ΔH (TeOI₂, g, 298) = ?10 ± 3 kcal/mol was derived from transport behaviour and the entropy S° (TeOI₂, g, 298) = 89.2 e.u. – obtained from molecular constants.     

Spectral characteristics of a 44-kHz arc discharge excited in an atmospheric-pressure argon flow

Results are presented from experimental studies of an ac (44-kHz) arc discharge excited in an atmospheric-pressure argon jet between two copper electrodes. The first (central) electrode is a water-cooled rod with an axial opening for argon injection, while the second electrode is a loop of a tube lying in a plane perpendicular to the axis of the central electrode. The argon radiation spectra are measured, and the characteristic intensity profiles of the spectral lines as functions of the distance from the end of the central electrode are determined. All the observed transitions in the 245-to 370-nm wavelength range are identified.     

Crystal nucleation, growth, and morphology of the synthetic malaria pigment beta-hematin and the effect thereon by quinoline additives: the malaria pigment as a target of various antimalarial drugs

The morphology of micrometer-sized beta-hematin crystals (synthetic malaria pigment) was determined by TEM images and diffraction, and by grazing incidence synchrotron X-ray diffraction at the air-water interface. The needle-like crystals are bounded by sharp {100} and {010} side faces, and capped by {011} and, to a lesser extent, by {001} end faces, in agreement with hemozoin (malaria pigment) crystals. The beta-hematin crystals grown in the presence of 10% chloroquine or quinine took appreciably longer to precipitate and tended to be symmetrically tapered toward both ends of the needle, due to stereoselective additive binding to {001} or {011} ledges. Evidence, but marginal, is presented that additives reduce crystal mosaic domain size along the needle axis, based on X-ray powder diffraction data. Coherent grazing exit X-ray diffraction suggests that the mosaic domains are smaller and less structurally stable than in pure crystals. IR-ATR and Raman spectra indicate molecular based differences due to a modification of surface and bulk propionic acid groups, following additive binding and a molecular rearrangement in the environment of the bulk sites poisoned by occluded quinoline. These results provided incentive to examine computationally whether hemozoin may be a target of antimalarial drugs diethylamino-alkoxyxanthones and artemisinin. A variation in activity of the former as a function of the alkoxy chain length is correlated with computed binding energy to {001} and {011} faces of beta-hematin. A model is proposed for artemisinin activity involving hemozoin nucleation inhibition via artemisinin-beta-hematin adducts bound to the principal crystal faces. Regarding nucleation of hemozoin inside the digestive vacuole of the malaria parasite, nucleation via the vacuole's membranous surface is proposed, based on a reported hemozoin alignment. As a test, a dibehenoyl-phosphatidylcholine monolayer transferred onto OTS-Si wafer nucleated far more beta-hematin crystals, albeit randomly oriented, than a reference OTS-Si.     

Arene Phosphorus-Containing Macrocyclic Crown Ethers: Last Studies

Abstract

The data on the synthesis, structures, and chemical properties of macrocyclic compounds containing endo-cyclic atoms of tri- and pentavalent phosphorus are summarized. Methods for the synthesis of the described macrocycles are reported. Peculiarities of structure, chemical properties, particularly formation of complexes, catalytic activity, and practical applications are analyzed. The bibliography includes 155 references.     

Synthesis and properties of 5-ferrocenyl-1H-pyrazole-3-carbaldehydes

New ferrocene derivatives - ethyl esters of 1-aryl-5-ferrocenyl-1H-pyrazole-3-carboxylic acids were synthesized. The corresponding aldehydes were obtained from acid esters in two steps. The reductive amination reaction of 5-ferrocenyl-1-phenyl-1H-pyrazole-3-carbaldehyde was studied. Several of these compounds were investigated by cyclic voltammetry. All of them exhibited a reversible one-electron oxidation-reduction wave owing to the ferrocene-ferricinium redox couple with a positive shift (0.51-0.69 V) compared with that of ferrocene (0.46 V). The X-ray crystal structure of the ethyl ether 1-(3-chloro-2-fluorophenyl)-5-ferrocenyl-1H-pyrazole-3-carboxylic acid is also presented.     

Redox properties of novel pyrrolidine derivatives containing sterically hindered phenol fragment

The method of cyclic voltammetry on a platinum electrode in acetonitrile is used to study the redox properties of a number of novel pyrrolidine derivatives containing a sterically hindered phenol fragment. It is found that the obtained derivatives of (3,5-di-tert-butyl-4-hydroxyphenyl)pyrrolidine-2-carboxylic acid are irreversibly oxidized in two stages with formation of a phenoxy radical. The structural analogue containing no phenyl fragment is irreversibly oxidized under similar conditions in a single stage. Formation of a stable phenoxy radical from synthesized (3,5-di-tert-butyl-4-hydroxyphenyl)pyrrolidines under PbO₂ oxidation is confirmed by ESR spectroscopy. Application of the synthesized compounds as antioxidant agents has been suggested.     

Study of the Anisotropic Elastoplastic Properties of β-Ga<Subscript>2</Subscript>O<Subscript>3</Subscript> Films Synthesized on SiC/Si Substrates

The structural and mechanical properties of gallium oxide films grown on silicon crystallographic planes (001), (011), and (111) with a buffer layer of silicon carbide are investigated. Nanoindentation was used to study the elastoplastic properties of gallium oxide and also to determine the elastic recovery parameter of the films under study. The tensile strength, hardness, elasticity tensor, compliance tensor, Young’s modulus, Poisson’s ratio, and other characteristics of gallium oxide were calculated using quantum chemistry methods. It was found that the gallium oxide crystal is auxetic because, for some stretching directions, the Poisson’s ratio takes on negative values. The calculated values correspond quantitatively to the experimental data. It is concluded that the elastoplastic properties of gallium oxide films approximately correspond to the properties of bulk crystals and that a change in the orientation of the silicon surface leads to a significant change in the orientation of gallium oxide.