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  • Inorganic Chemistry  (19)
  • Column liquid chromatography  (4)
  • Enantiomeric olefins  (2)
  • hydrogen bonds  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Molecular dynamics simulation of crystalline β-cyclodextrin dodecahydrate at 293 K and 120 K (1987)
    Springer
    European biophysics journal 15 (1987), S. 211-224 
    Details
    ISSN: 1432-1017
    Keywords: β-cyclodextrin dodecahydrate ; molecular dynamics simulation ; hydrogen bonds ; empirical force field ; water molecule diffusion ; positional disorder
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Molecular dynamics (MD) simulations for crystalline β-cyclodextrin dodecahydrate (β-CD) at two different temperatures, 293 K and 120 K, have been performed using the GROMOS program package. The calculated structural properties are compared to those obtained from neutron diffraction studies of this system at the quoted temperatures. The simulation was carried out over a period of 20 ps on four unit cells containing 8 β-CD molecules and 96 water molecules, whereby all atoms were allowed to move. At room temperature, the experimental positions of the (non-hydrogen) glucose atoms are reproduced within 0.034 nm, a value which is smaller than the experimental (0.041 nm) or simulated (0.049 nm) overall root mean square (rms) positional fluctuation. The corresponding numbers for the low temperature study are 0.046 nm, 0.019 nm and 0.022 nm. At both temperatures the experimentally observed degree of anisotropy of the atomic motions is also found in the simulations. The comparison of a variety of structural properties leads to the conclusion that the molecular model and force field used are able to simulate the cyclodextrin system very well. Experimentally observed differences in properties as a function of number of glucose units in the CD molecule (α-CD, 6 versus β-CD, 7) and as a function of temperature are qualitatively reproduced by the simulations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00577069
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  • 2
    Electronic Resource
    Electronic Resource
    A molecular dynamics simulation of crystalline α-cyclodextrin hexahydrate (1987)
    Springer
    European biophysics journal 15 (1987), S. 197-210 
    Details
    ISSN: 1432-1017
    Keywords: α-cyclodextrin hexahydrate ; molecular dynamics simulation ; empirical force field ; hydrogen bonds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract The structure of crystalline α-cyclodextrin (α-CD) hexahydrate, form I (C36H60O30·6H2O, space group P212121) is experimentally so well determined by X-ray and by neutron diffraction analyses that the positions of all the hydrogen atoms are available. This provides an opportunity for testing an empirical force field that is currently used in simulations of protein and nucleic acid structures by performing molecular dynamics studies employing the GROMOS program package on a system of 4 unit cells containing 16 α-CD molecules and 96 water molecules. A detailed comparison of the simulated and experimentally determined crystal structures shows that the experimental positions of the α-CD atoms are reproduced within 0.025 nm, well within the overall experimental accuracy of 0.036 nm; that the water molecules are on average within 0.072 nm from their experimental sites, with two thirds reproduced within experimental accuracy by the calculations; that high correlation is produced, between the occurrence of simulated and experimentally observed hydrogen bonds. The good agreement between simulated and experimental results suggests that the tested force field is reliable.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00577068
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  • 3
    Electronic Resource
    Electronic Resource
    Preparative LC separation and isolation of enantiomerically pure olefins (1984)
    Springer
    Chromatographia 18 (1984), S. 119-124 
    Details
    ISSN: 1612-1112
    Keywords: Enantiomeric olefins ; Platinum complexes ; Ligand exchange ; Preparative gas chromatography ; Preparative column-liquid chromatography ; Column switching
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Diastereomer formation by the reaction of chiral olefins with optically active platinum complexes followed by LC separation of the diastereomers, and on-line or off-line release of the olefins from the complexes by ligand exchange yield optically pure enantiomers. The 100% dextrostetatory enantiomer of exo-2-vinylbicyclo[2.2.1]heptane (vinylnorbornane) could be isolated by an off-line method and was used for polarimetric measurements before and after preparative scale gas chromatographic clean-up. The initial valuable platinum complex could be easily recovered without loss.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02258766
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  • 4
    Electronic Resource
    Electronic Resource
    Liquid chromatography with and of platinum complexes (1981)
    Springer
    Chromatographia 14 (1981), S. 559-566 
    Details
    ISSN: 1612-1112
    Keywords: Reversed phase HPLC ; Normal phase HPLC ; Platinum complexes in mobile phase ; Enantiomeric olefins ; Diasteromeric complexes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Reversed-phase, high-performance liquid chromatography (HPLC) on chemically bonded C18-phases with acetonitrile-water mobile phases, contianing platinum complexes like Zeise's salt C2H4PtCl3, the amine derivative C2H4−PtCl2−NH2−CH(CH3)−C6H5 or the amino acid compound C2H4−PtCl−OOC−CH(N(CH3)2)−C6H5 by analogy with argentation chromatography, was used to increase selectivity for the separation of various types of olefins, amines and heterocyclic compounds. On the other hand, normal-phase adsorption chromatography on silica with n-heptane, dichloromethane and n-propanol mobile phases proves to be an ideal tool for the analytical and preparative separation of diastereomeric platinum complexes of olefins, introduced by Gil-Av, that can be easily preparedin vitro, by the reaction of C2H4−PtCl−OOC−CH(N(CH3)2)−C6H5 with optically active olefins in CH2Cl2. The preparation of the intitial complex as well as its application to the separation of several interesting types of enantiomeric olefins is described and discussed. The number and amount of separable diastereomers formed by the above reaction is strongly influenced by sterical effects. By comparison of the chromatographic pattern of either racemic or partly racemic mixtures, it is possible to decide, which peaks belong to one or the other enantiomeric form of the olefin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02262884
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  • 5
    Electronic Resource
    Electronic Resource
    New polymer coated anion-exchange HPLC-phases: Immobilization of poly (2-hydroxy, 3N-ethylenediamino) butadiene on silica and alumina (1987)
    Springer
    Chromatographia 23 (1987), S. 435-441 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Anion-exchange stationary phases ; Polymer coating ; Cross-linking
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary PHEB=POLY(2-hydroxy, 3N-ethylenediamino)butadiene has been synthesized. This unsaturated pre-polymer can be immobilized on different, preferably inorganic supports of suitable porosity such as silica or alumina by cross-linking. Weak anion-exchange phase are obtained. Such phases do not have the disadvantages of organic polymeric phases, regarding pressure stability and swelling by solvent influence. The ion-exchange capacity and the retentivity of IE-separations can deliberately be varied via the thickness of the cross-linked polymer layer. Alumina can also be coated with PHEB applying the same cross-linking procedure. Such phases exhibit an exceptional chemical stability even when operated with mobile phases at very high pH-values. Separations of excellent selectivity are achieved for inorganic anions, as well as with mixtures of aliphatic and aromatic free acids also including hydroxy- (mono- or poly)carboxylic acids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02311821
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  • 6
    Electronic Resource
    Electronic Resource
    Poly(vinylpyrrolidone)-coated silica: A versatile, polar stationary phase for HPLC (1986)
    Springer
    Chromatographia 21 (1986), S. 573-582 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Polyvinylpyrrolidone-coated silica gel ; Separation of polar compounds ; Separation of proteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Poly(vinylpyrrolidone) (PVP) is immobilized on both, small- and large-pore silicas by thermal treatment, γ-radiation, or peroxide initiated polymerization. The hydrolytic stability of such a highly polar stationary phase significantly exceeds that of a comparable phase prepared by the chemical reaction of silica with a pyrrolidone ethyl dimethylchlorosilane silanization reagent. The properties of the different PVP-silicas are evaluated by elemental analysis, spectroscopy, and chromatography. Columns of PVP-silica packings can be used in several modes: a) under normal-phase conditions as a polar bonded stationary phase, b) under reversed-phase conditions, for the separation of organic proton-donor and hydrogen-bonding compounds, c) for the aqueous size exclusion chromatography of proteins, and d) with salt gradients for the hydrophobic interaction chromatography of proteins. The minimum observable reduced plate-height of PVP-silica columns is about 3. Double-layer polymer coating experiments using PVP-silica covered with poly(methyloctadecylsiloxane) have been performed to study diffusion and shielding effects of different polymer layers in the stationary phase. Depending on separation conditions, one or the other polymer governs the retention process. A mixed selectivity was observed in a reversed phase mode with acidic eluents.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02311839
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  • 7
    Electronic Resource
    Electronic Resource
    HPLC-separation of enantiomers using quinine, covalently bonded to silica as stationary phase (1988)
    Springer
    Chromatographia 25 (1988), S. 265-271 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chiral phases ; Polymer coating ; Quinine substituted polysiloxanes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Stationary phases for chiral separations have been synthesized by chemical modification of porous small particle silica using new procedures of fixation of the chiral moiety. So called pre-polymers of the methylpolysiloxane polysiloxane type are immobilized on silica surfaces by different procedures. These pre-polymers are substituted by chiral groups. Their synthesis is done externally i.e. not in-situ on the support surface. The immobilization on the silica surface is achieved by crosslinking and/or by chemical bonding. Anchor groups within the pre-polymer (e.g. SiH) as well as on the silica surface (SiOH) give rise to the chemical bonding therewith. Chiral phases with quinine as the chiral moiety were obtained which show high separation efficiency as well as chemical stability, in addition to the enantiomeric selectivity required for the separation of certain types of aliphatic and aromatic alcohols.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02324699
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  • 8
    Electronic Resource
    Electronic Resource
    Zur Kenntnis der Chemie der Metallcarbonyle in flüssigem Ammoniak. IV. Über Neue Substitutionsprodukte des Cr(CO)6 mit aromatischen Aminen (1959)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 300 (1959), S. 51-60 
    Details
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: By interaction of alkali pentacarbonyl chromates(-II) with aromatic mono-, di-, and triamines at room temperature only pentacarbonyl amine chromium(0) compounds are formed. Wheras m- and p-phenylene diamine are linked with two and 1, 3, 5-triaminobenzene with three Cr(CO)5-groups, o-phenylene diamine forms a corresponding compound with only one Cr(CO)5-group. Unlike ethylene diamine or cyclohexane diamine(1,2) o-phenylene diamine does not give a tetracarbonyl chromium(0) compound.
    Notes: Bei der Umsetzung von Alkali-pentacarbonyl-chromaten(-II) mit wäßrigen Lösungen von aromatischen Mono-, Di- und Triaminen bei gewöhnlicher Temperatur erhält man stets Pentacarbonyl-amin-chrom(0)-verbindungen, die sich als echte Substitutions-produkte des Cr(CO)6 erweisen. Während m- und p-Phenylendiamin zwei und 1,3,5-Triaminobenzol drei Cr(CO)5-Gruppen zu binden vermögen, erhält man im Falle des o-Phenylendiamins eine entsprechende Verbindung mit nur einer Cr(CO)5-Gruppe. Insbesondere entsteht bei letzterem - im Gegensatz zum Äthylendiamin - keine Tetracarbonyl-chrom(0)-verbindung. Eine solche bildet sich hingegen, wenn man an Stelle des o-Phenylendiamins das hydrierte o-Phenylendiamin, also Cyclohexandiamin(1,2), zur Reaktion bringt.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19593000105
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  • 9
    Electronic Resource
    Electronic Resource
    Das erste Oligo-Oxo-Aluminat: Na14[Al4O13] (1983)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 507 (1983), S. 155-162 
    Details
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The First Oligo-Oxo-Aluminate: Na14[Al4O13]Colourless single crystals of Na14[Al4O13] are formed by reaction of Na2O and Al2O3 in a closed Ni-cylinder at 980 K. The compound is very sensitive against moisture. Na14[Al4O13] crystalizes in the monoclinic space group P21/c with 2 formula units (a = 599.7, b = 2704.0, c = 596.9 pm, β = 120.1°). The characteristic feature of the structure, the anion [Al4O13]14-, is built of four AlO4-tetrahedra, sharing vertices. The connection of these groups by the counter-cations is discussed.
    Notes: Farblose Einkristalle von Na14[Al4O13] bilden sich bei der Reaktion von Na2O mit Al2O3 bei 780 K im geschlossenen Ni-Bömbchen. Die Substanz ist stark feuchtigkeitsempfindlich. Na14[Al4O13] kristallisiert in der monoklinen Raumgruppe P21/c mit 2 Formeleinheiten (a = 599,7, b = 2704,0, c = 596,9 pm, β = 120,1°). Die charakteristische Baugruppe der Struktur ist das erstmals erhaltene Anion [Al4O13]14-, welches von vier über Ecken verknüpften AlO4-Tetraedern gebildet wird. Die Verknüpfung dieser Gruppen durch die Gegenkationen wird besprochen.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19835071219
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  • 10
    Electronic Resource
    Electronic Resource
    Das erste Oligo-Oxo-Aluminat: Na14[Al4O13] (1984)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 512 (1984), S. 240-240 
    Details
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19845120525
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