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  • 1
    ISSN: 1612-1112
    Keywords: Gas-solid chromatography ; Graphitized thermal carbon black ; Thermodynamics of adsorption ; Nitrogen compounds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary To study the role of the nitrogen atom in various valence states in the adsorption of nitrogen-containing molecules on the surface of hydrogen-treated graphitized thermal carbon black (HGTCB) gas chromatography was applied to determine the thermodynamic characteristics of adsorption: Henry's constants and heats of adsorption at zero surface coverage of nitriles, amines and indols on HGTCB. Adsorption characteristics of nitrogen-containing organic compounds and corresponding hydrocarbons are compared. It is shown that the logarithm of the retention volume and the heat of adsorption of n-alkylamines and n-alkylnitriles linearly depend on the number of carbon atoms in the molecule and on the average polarisability of the molecule. Relationship has been established between the Henry's constant as well as the heat of adsorption and the geometry of the molecule's disposition on HGTCB surface. Examples are given for the separation of a number of amines on the basis of the geometry of their molecules.
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  • 2
    ISSN: 1612-1112
    Keywords: Gas Chromatography ; Graphitized thermal carbon black ; Polycyclic aromatic hydrocarbons ; Structure-retention relationships
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary On efficient glass capillary columns packed with graphitized thermal carbon black (GTCB) the stereoisomers of aromatic and saturated tricyclic hydrocarbons are completely separated and identified. The Henry's adsorption constants of the individual isomers were determined from mixtures at different temperatures. Five isomers of perhydroanthracene, five isomers of perhydrofluorene, two isomers of perhydrophenalene, four isomers of perhydroacenaphthene, as well as phenalene, dihydrophenalene, acenaphthene and acenaphthylene were investigated. The increase of the hydrogenization degree of unsaturated tricyclic hydrocarbons reduces the retention. Among the saturated tricyclic isomers the retention becomes shorter with the larger bending of the molecules, i.e. from the molecule having more equatorial bonds to the molecules having more axial connections. The experimentally determined Henry's constants were qualitatively compared with the structure of the separated molecules.
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  • 3
    ISSN: 1612-1112
    Keywords: Gas adsorption chromatography ; Graphitized thermal carbon black ; Indan ; Indan-type hydrocarbons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Es werden die Werte der Retentionsvolumina, der Retentionsindices und andere thermodynamische Adsorptionscharakteristiken von zehn Indan- und Inden-Kohlenwasserstoffen mit 9–11 Kohlenstoffatomen auf graphitiertem thermischem Ruß (GTR) bestimmt. Es wurde festgestellt, daß auf GTR die Kohlenwasserstoffe der Inden-Reihe am stärksten adsorbiert werden und am schwächsten cis-Hydrandan, was mit den Besonderheiten der geometrischen Struktur dieser Verbindungen zusammenhängt. Es wird die Möglichkeit der Anwendung von GTR für die vollständige Trennung der cis- und trans-Isomeren von Hydrindan gezeigt.
    Notes: Summary The retention volumes, retention indices and other thermodynamic values characteristic of the adsorption of ten indan-hydrocarbons having 9–11 carbon atoms were determined on graphitized thermal carbon black (GTCB). It is shown that GTCB adsorbs strongest the hydrocarbons of the indan series and weakest cis hydrindan. This is related to the peculiarities of the geometric structure of the compounds. The possibility of the application of GTCB for the complete separation of cis and trans hydrindan is shown.
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  • 4
    ISSN: 1612-1112
    Keywords: Gas adsorption chromatography ; Graphitized thermal carbon black ; Cyclic ethers and ketones ; Atom-atom oxygen … carbon potentials
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The paper is concerned with molecular-statistical determination of retention volumes of oxygen-containing organic substances such as cyclic ethers and ketones by presenting the potential energy of intermolecular interaction of the molecules with a monoatomic adsorbent having homogeneous flat surface (graphitized thermal carbon black) as a sum of atom-atom potentials. In order to eliminate the specific interactions of ethers and ketones with the traces of surface oxygen compounds on graphitized thermal carbon black, the latter was treated additionally with hydrogen. Comparison is made between the experimentally measured retention volumes and the Henry constants calculated for reference molecules of ethers (dioxane) and ketones (cyclohexanone) to correct the atom-atom potentials. It is shown that the atom-atom potentials obtained for the reference molecules can be used for other ethers and ketones of known structure with the subsequent calculation of the corresponding values of the retention volumes in terms of molecular statistics. When the structure is not known its parameters are optimized using the chromatostructural method (chromatoscopy). The calculated heat of adsorption values agree well with those determined from the chromatographic measurements. Chromatograms showing the full separation of mixtures of the ethers and ketones studied were obtained.
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  • 5
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Eine Aminolyse von makroporösen Copolymeren aus Glycidylmethacrylat und Ethylendimethacrylat führte zu Sorbentien mit einem unterschiedlichen Gehalt an Amino-und Hydroxygruppen. Es wurde die Abhängigkeit zwischen strukturellen Parametern und der Schwefeldioxidsorption auf der einen und der Konzentration des Vernetzungsmittels und der porogenen Lösungsmittel in der Polymerisationsmischung auf der anderen Seite untersucht. Die Schwefeldioxidsorption hängt von der geometrischen Struktur des Sorbens, der Konzentration, der chemischen Struktur und der Erreichbarkeit der funktionellen Gruppen ab.
    Notes: Macroporous copolymers of 2,3-epoxypropyl methacrylate and ethylenedimethacrylate modified by aminolysis yielded sorbents with various contents of amino and hydroxy groups. The dependences of structural characteristics of these sorbents and of the sorption of sulphur dioxide on the content of crosslinking agent and on the cyclohexanol/dodecanol ratio used as the porogenic medium in the preparation of copolymers were investigated. The sorption of sulphur dioxide depends on the geometrical structure of the sorbent, concentration, chemical structure and accessibility of functional groups.
    Additional Material: 7 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 559 (1988), S. 171-181 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Über die Umsetzung der Di- und Tetrafluoride des Xenons mit Fluoriden der AlkalimetalleDie Umsetzung von XeF2 und XeF4 mit Verbindungen des Typs MF (M = Na, K, Rb, Cs) wird untersucht. Es bilden sich dabei Hexafluoroxenate(IV) mit der Summenformel M2XeF6, die das oktaedrische Anion XeF62- enthalten. Cs2XeF6 und Rb2XeF6 bilden monokline Kristalle (a0 = 853,7(5); b0 = 669,6(2); c0 = 843,6(5) pm; β = 121,7(1)° für Cs2XeF6 und a0 = 812,6(4); b0 = 631,9(2); c0 = 795,6(4) pm; β = 121,5(1)° für Rb2XeF6). K2XeF6: tetragonal mit a0 = 868,8(2); c0 = 747,8(2) pm; Na2XeF6: hexagonal mit a0 = 642,1(3); c0 = 844,8(5) pm. Es wird gezeigt, daß sich die Verbindungen M2XeF6 inkongruent in wasserfreiem HF lösen, wobei sich unter anderem das Solvolyseprodukt XeF4 bildet. Es wird nachgewiesen, daß die Thermolyse von M2XeIVF6 und M2XeVIF8 unter ähnlichen Bedingungen abläuft.
    Notes: Interaction of XeF2 or XeF4 with MF (M = Na, K, Rb, Cs) has been studied. Hexafluoroxenates(IV) M2XeF6 containing the octahedral XeF62- anion (in accordance with spectroscopy data) were formed in the reaction. Cs2XeF6 and Rb2XeF6 form monoclynic crystals (a0 = 853.7(5); b0 = 669.6(2); c0 = 843.6(5) pm; β = 121.7(1)° and a0 = 812.6(4); b0 = 631.9(2); c0 = 795.6(4) pm; β = 121.5(1)°, respectively). K2XeF6 has a tetragonal lattice (a0 = 868.8(2); c0 = 747.8(2) pm), while Na2XeF6 has a hexagonal one (a0 = 642.1(3); c0 = 844.8(5) pm). M2XeF6 is shown to dissolve in unhydrous HF incongruently, one of the solvolitic products being XeF4. Thermolysis of M2XeIVF6 and M2XeVIF8 were shown to proceed under similar temperatures.
    Additional Material: 4 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 559 (1988), S. 182-190 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Über die Säure-Base-Eigenschaften des Di- und Tetrafluorxenons in Reaktionen bei erhöhten TemperaturenEs wurde die Reaktion von Xenondifluorid und Xenontetrafluorid mit Fluorkomplex-Verbindungen verschiedener Übergangsmetalle bei erhöhter Temperatur untersucht. Unter diesen Bedingungen wurde die Bildung von Anionenkomplexen M2XeIVF6 festgestellt. Es wurde gezeigt, daß XeF4 unabhängig davon, ob es direkt in die Reaktion eingeführt wird oder dort aus XeF2 entsteht, zwei typische Eigenschaften aufweist: die eines Oxydationsmittels (〉 300°C) und einer Säure (zwischen 150°C und 300°C). Das Reaktionsverhalten des XeF4 hängt ferner von den Eigenschaften des Reaktionspartners ab. Die Eigenschaften der Xenonfluoride als Lewis-Säuren folgen der Reihe: XeF6 ≈ XeF4 ≫ XeF2.
    Notes: Reaction of xenon di- and tetrafluoride with different transition element fluorocomplexes at high temperatures has been studied. The formation of XeIV anionic complexes M2XeF6 has been found. XeF4 is shown to reveal two kinds of properties: oxidative (higher than 300°C) and acidic (between 150-300°C), independently whether it was initially introduced into the system or arised in it from XeF2. The reaction path of xenon tetrafluoride is shown to depend upon the other reagent properties. The conclusion is made that Lewis acidic properties of xenon fluorides decrease as follows: XeF6 ≈ XeF4 ≫ XeF2.
    Additional Material: 1 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 474 (1981), S. 233-240 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Schwingungsspektren kristalliner Hexachlorocerate(IV), R2CeCl6Eine vollständige Zuordnung aller Fundamentalbanden in den Spektren kristalliner R2CeCl6, die zu den Ce—Cl-Schwingungen gehören, wurde unter Benutzung von Daten über Kombinationsschwingungen und im Raman-Spektrum aktiver Oberschwingungen vorgenommen. Die Vermutung über die Existenz einer isolierten [CeCl62-]-Gruppe, die in Kristallen mit einer genügend hohen Gitterpunktsymmetrie eine oktaedrische Struktur aufweist, konnte bestätigt werden. Auf der Grundlage des experimentellen Materials und seiner Deutung wird die Vermutung über das Auftreten eines Pseudo-Jahn-Teller-Effektes in der Hexachloroceraten(IV) geäußert.
    Notes: A complete assignment of all fundamentals in the spectra of crystalline R2CeCl6 belonging to the Ce—Cl vibrations was undertaken using data about combination bands and active in the Raman spectrum overtones. The assumption of the presence of a separate [CeCl62-] group possessing an octahedral structure in crystals with a sufficient high site symmetry has been confirmed. Based on the experimental material and its interpretation a presumption concerning the appearence of a pseudo-Jahn-Teller effect in the hexachlorocerates(IV) was supposed.
    Additional Material: 2 Ill.
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  • 9
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A tool was developed for enhancement of plasmid penetration into an intact cell, based on increasing DNA hydrophobicity via inclusion into a soluble interpolyelectrolyte complex (IPC) with polycations. The characteristics of formation of DNA IPC with synthetic polycations [poly(N-ethyl-4-vinylpyridinium)bromide (PVP) and PVP modified with 3% of N-cetyl-4-vinylpyridinium units (PVP-C)] were studied using ultracentrifugation and polyacrylamide gel electrophoresis methods. The conditions were established under which the mixing of DNA and polycation aqueous solutions results in the selfassembly of soluble IPC species. Incorporation of DNA into IPC results in the enhancement of DNA binding with isolated Bacillus subtilis membranes. A considerable increase in the efficiency of transformation of B. subtilis cells with pBC16 plasmid resulted from incorporation of the plasmid into the IPC with PVP and CVP.
    Additional Material: 6 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 81-84 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A new approach to the quantitative evaluation of the thickness hi and the volume fraction Vi of the interfacial layer in polyimide coatings has been developed using the model of a one-sided polymer coating as a three-phase system (a substrate, an interfacial layer and a polymer matrix) and the method of differential scanning calorimetry. The new approach is characterized by the fact that a “pure” polymer matrix is modeled with the help of free films obtained on mercury. The formulas for the calculation of the thickness and volume fraction of the interfacial layer have been proposed. The value hi has been determined in polymer coatings of different thicknesses on aluminium foil. This parameter has been shown to be independent of the film thickness if the latter is not larger than the length of the interfacial layer. An assumption has been made about the “mechanical” origin of thick (〉 1-5 μm) interfacial layers, and their relaxation character has been revealed.
    Additional Material: 4 Ill.
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