Molecular and crystal structure of the reaction product of dodecahydro-7,8-dicarba-Nido-undecaborat (1−) with 4-methylpyridine,C2B9H11(NC5H4Me)

The title compound has been studied by an X-ray structure analysis (a CAD-4 diffractometer, MoK, graphite monochromator, /2 scan, 2 _max, direct methods, 884 reflections R=0.0416). The crystals are orthorhombic with a=20.326, b=8.828, c=7.3872 Å, V=1325.6 ų, and Z=4. C₈H₁₈B₉N, space group Pnam, d_calc=1.130 g/cm³, d_exp=1.130 g/cm³. The compound is a molecular complex. The main feature of its crystal structure is the coexistence of two asymmetric mirror isomers which have the same pyridine cycle and the same atoms of the carborane skeleton (excluding C7, H7C, and H34). The methyl group has a disordered orientation in two positions. The complexes are linked by van der Waals interactions.Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 34, No. 4, pp. 149–153, July–August, 1993.Translated by T. Yudanova     

Substituted dienic 1,3-dioxolan-2-ones and bis(1,3-dioxolan-2-ones)

Alkylthio-substituted dienic 1,3-dioxolan-2-ones and bis(4,4-diorganyl-5-methyli-dene-1,3-dioxolan-2-ones) were obtained in high yields by the reaction of 2-methyl-6-alkylthio-5-hexen-3-yn-2-ols and tertiary diacetylenic glycols with carbon dioxide under pressure in the presence of catalytic amounts of triethylamine and monovalent copper salts.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1617–1619, December, 1979.Original article submitted January 24, 1979.     

Structure and Electrochemical Properties of Cation-Exchange Membranes Based on Partially Imidized Polyamidoacid

The transport of water molecules and the distribution of functional groups in polyamidoacid carboxyl-containing cation-exchange membranes based on pyromellitic acid are studied by NMR and ESR techniques. It is shown that the self-diffusion coefficients of water differ in the gel and intergel regions. Structural parameters of conducting channels in the gel regions are determined. In electrodialysis of one-component and binary solutions, polyamidoacid membranes possess higher transport numbers and separation coefficients of counterions that are less hydrated in solution.     

Crystal structure of di (1-n-dodecylpyridine) decahydro-closo-decaborate(2-) (C5H5N-C12H25)2[B10H10]

Using X-ray analysis, we have determined the crystal structure of di(1-n-dodecylpyridine) decahydrocloso-decaborate(2-), (py-C₁₂H₂₅)₂[B₁₀H₁₀] (I), a yellow salt-like substance obtained by reaction of (py-C₁₂H₂₅)Br and K₂[B₁₀H₁₀] in an aqueous solution. Compound I melts at 125⁰ without decomposition and luminesces under ultraviolet radiation (λ_max=555 nm at 298 K). In I, quaternary pyridine bases, containing a hydrocarbon radical with the C₁₂ chain, are combined with the closo-cluster hydroborate anion [B₁₀H₁₀]^2-. This results in a charge transfer structure having shortened nonvalent (equatorial B) H.…H(C of pyridine) contacts of 2.41(8) Å. Crystals I are orthorhombic with a=8.584 (1), b=7.739(1), c=31.183(5) Å, V_cell=2071.4(5) ų, space group Pnmm, Z=2, d_calc=0.986 g/cm³ (a Syntex P2₁ automatic diffractometer, λCUK_α, N_msd/used=1654/711, R_aniso=0.076, R_w=0.080, w=1/(σ(F_obs)²+0.0007·F _obs ² ). Substantial changes are observed in the vibration range of the valent B?H bonds in the IR spectrum of I as compared to that of pure ionic K₂[B₁₀H₁₀], confirming the interaction.     

The large-scale vortex structures in plasma-like media and the electric explosion of conductors

Formation of large-scale hydrodynamic convective patterns in plasma-like current-carrying media is considered. This process is shown to be described by the same equations, as Benard rolls, except that a temperature field must be replaced by a magnetic field. A simple low-mode model of spatial pattern formation for a case of cylindrical liquid-metal conductor with current is proposed and investigated. Nonlinear interaction of perturbations of the magnetic field and the velocity field results in an increase of effective conductor resistance even when transport coefficients are constant. In our opinion, it is this instability, that is of first importance at the initial stages of the electric explosion of conductors. In particular, it leads to conductor stratification and electric current interruption. (c) 1996 American Institute of Physics.     

Effect of the size of the aliphatic chain on the NMR spectra and the electrical conductivity of melts of alkali metal alkanoates in alkanoic acids

The dependence of NMR spectra of ⁷Li, ²³Na, ¹³³Cs and of the conductivity of melts of lithium, sodium, and cesium alkanoates in melts of alkanoic acids on the length of the aliphatic chain of the anion has been studied. As the anion size increases, chemical shifts of ²³Na and ¹³³Cs nuclei toward weak fields and ⁷Li nuclei toward strong fields are observed. The nature of the chemical shifts of alkali metal nuclei and of the electricity transport characteristic in the studied systems is discussed in connection with the nature of cation-anion interactions and the size and degree of free rotation of the anion.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 29, No. 1, pp. 81–87, January–February, 1993.     

Geometric,Spectroscopic, and Magnetic Characteristics of [Tris(1,10-phenanthroline)manganese](2+) 1,2;1′,2′-<Emphasis Type="Italic">trans</Emphasis>-Bis[nonahydro-<Emphasis Type="Italic">closo</Emphasis>-decaborate](2−) Bis(dimethylformamide)

[Tris(1,10-phenanthroline)manganese](2+) 1,2;1′,2′-trans-bis[nonahydro-closo-decaborate](2?) bis(dimethylformamide) containing the complex anion [MnPhen₃]²⁺ with the paramagnetic central Mn atom and the [B₂₀H₁₈]^2? anion formed by fusion of two closo clusters B₁₀H₉ was synthesized and characterized by single crystal X-ray diffraction and by IR, X-ray photoelectron, and Raman spectroscopy.     

Electrical conductivity in single-crystals of vanadium oxide bronzes

Single-crystal electrical conductivity of vanadium oxide bronzes of the type M_xV₂O₅ (β-phase), where M = Li, Na, K has been studied from 300 to 900°K. These compounds are found to exhibit a reversible semiconductor-metal transition along [010] in the region of 340°K. The phase transition observed seems to be caused by vanishing of the activation energy of carrier mobility due to the shift of some vanadium atoms in the planes perpendicular to the B axis.     

Preparative gas-solid adsorption chromatography. Part II. Selection of optimal conditions for separation in preparative chromatography

Summary The paper discusses the effects of the flow rate and the nature of the carrier gas, and the value of the Henry temperature coefficient on the capacity and effciency of preparative gas-solid adsorption columns.The theoretical relationship between the height equivalent of a theoretical plate (HETP) and the experimental parameters under overloaded conditions was obtained byDe Wet andPretorius [1] and somewhat modified by us [2]. Although it was derived under the assumption that the sorption isotherm is linear, the equation was shown to be in qualitative agreement with the experimental results when the separation took place in a partition column.Consequently we investigated the applicability of this equation for separation on gas-solid adsorption columns containing modified silica, further the optimum characteristics of the adsorbents and the optimal separation conditions. The dependence of the capacity on the separation conditions, theoretically derived by us in an earlier paper [3] has also been studied.

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Präparative Adsorptions-Fest-Gas-Chromatographie. Teil II: Wahl der optimalen Trennbedingungen in der präparativen Chromatographie

Zusammenfassung Die Arbeit befaßt sich mit der Wirkung von Strömungsgeschwindigkeit und Art des Trägergases, sowie mit dem Wert des Temperatur-Koeffizienten nach Henry auf die Kapazität und Wirksamkeit von Adsorptionssäulen für die präparative Fest-Gas-Chromatographie. Die theoretische Beziehung zwischen Bodenzahl (HETP) und Versuchsbedingungen bei Überladung wurde vonDe Wet undPretorius [1] emittelt und von uns etwas abgewandelt [2]. Obwohl sie unter der Voraussetzung einer linearen Adsorptionsisotherme abgeleitet wurde, zeigte die Gleichung gute Übereinstimmungmit den experimentell erhaltenen Ergebnissen bei der Trennung in einer Verteilungssäule. Daraufhin untersuchten wir die Anwendbarkeit dieser Gleichung für Trennungen auf Adsorptionssäulen für die Gas-Fest-Chromatographie, die mit modifiziertem Silicagel gefüllt waren; weiterhin versuchten wir die optimalen Eigenschaften der Adsorbentien und die optimalen Trennbedingungen zu ermitteln. Die Abhängigkeit der Belastbarkeit von den Trennbedingungen, die in einer früheren Arbeit [3] von uns schon theoretisch abgeleitet worden war, wurde ebenfalls untersucht.

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Chromatographie d'adsorption gaz-solide prépartive. 2ème Partie: Sélection des conditions optimales de séparation en chromatographie préparative

Résumé Dans ce travail on étudie les effets de la vitesse, de la nature du gaz vecteur, ainsi que de la valeur du coefficient de température selon Henry, sur la capacité et l'efficacité de colonnes adsorbantes en chromatographie préparative gaz-solide. La relation théorique entre la hauteur équivalente d'un plateau théorique (HETP) et les paramètres expérimentaux, dans des conditions de surcharge, a été établie parDe Wet etPretorius [1] et légèrement modifiée par nous [2]. Bien que cette relation füt obtenue en supposant que l'isotherme d'adsorption est linéaire, on trouve une bonne concordance qualitative avec les résultats expérimentaux de la chromatographie de partage. Par conséquent nous avons étudié la validité de cette équation pour des séparations sur colonnes adsorbantes en chromatographie gaz-solide (silice modifié); en outre nous avons essayé d'établir les caractéristiques optimales des adsorbants et les conditions de séparation optimales. On a étudié la relation existant entre la capacité et les conditions de séparation, en tenant compte des équations théoriques établies par nous dans un travail antérieur [3].