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  • 1
    Electronic Resource
    Electronic Resource
    Conformational analysis of dimethylphosphate with quantum-mechanical and classical methods (1978)
    Springer
    Theoretical chemistry accounts 50 (1978), S. 169-179 
    Details
    ISSN: 1432-2234
    Keywords: Dimethylphosphate, conformational analysis of ∼
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In order to shed light on the conformational behavior of polynucleotide chains, and in particular to clarify the origins of the barriers to internal rotation in the phosphodiester linkage, we computed, with a quantum-mechanical ab initio procedure, the energies associated to 86 combinations of the two torsion angles in the dimethylphosphate anion (CH3O)2PO2 −, and then we sought for an analytical expression apt to reproduce these energies with the highest possible accuracy. An excellent agreement (standard deviation of the fitted energies from the ab initio energies 0.28 kcal/mole) with the quantum-mechanical calculations was reached with a potential consisting of four terms: 1) a 6–12 Lennard-Jones contribution, in which different parameters are used to describe the interactions of methyls with the ester oxygens and with the anionic oxygens; 2) a contribution with twofold periodicity, accounting for the anomeric effects connected to the interactions between the lone pair electrons and the polar bonds of phosphorus with the anionic oxygens; 3) a contribution with threefold periodicity, representing the usual bond-staggering term; and 4) a Coulombic contribution, arising from electrostatic interactions between partially charged atoms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00550189
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  • 2
    Electronic Resource
    Electronic Resource
    Quantum calculation of the intrinsic torsional barrier of C-C and C-O bonds (1982)
    Springer
    Theoretical chemistry accounts 62 (1982), S. 29-38 
    Details
    ISSN: 1432-2234
    Keywords: n-butane ; Internal rotation in ∼ ; Methyl ethyl ether ; Internal rotation in ∼
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract PCILO and ab initio calculations have been performed to investigate the energies associated to rotation about the central bond in n-butane and methyl ethyl ether. Quantum mechanical energies have been fit to a classical intramolecular force field, containing torsional and nonbonded (Lennard-Jones 6–12 plus Coulomb) contributions, with a standard deviation comprised between 0.03 and 0.09 kcal mol−1. Two conditions have proved indispensable to reach such level of accuracy: (a) the use of a torsional potential with threefold periodicity, which corrects for the part of the rotation barrier not covered by van der Waals repulsions and may be interpreted as bond-bond repulsion; (b) the introduction in the force field for ethers of terms accounting for orbital interaction effects of different nature than the normal molecular mechanics nonbonded interactions; these terms are represented either by low order rotational potential functions or preferably by interactions of atoms simulating lone-pair orbitals and bonded to oxygen in such a way as to render it sp 3-hybridized. According to ab initio, the height of the threefold torsional potential about C-C and C-O bonds is comparable and is of the order of 3 kcal mol−1. According to PCILO, it is larger for C-C (ca. 1.5 kcal mol−1) than for C-O (ca. 0.5 kcal mol−1).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00551051
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  • 3
    Electronic Resource
    Electronic Resource
    Molecular orbital computations of the conformational energy of ethyl methyl phosphate (1981)
    Springer
    Theoretical chemistry accounts 60 (1981), S. 41-51 
    Details
    ISSN: 1432-2234
    Keywords: Ethyl methyl phosphate, conformational analysis of ∼ ; Intramolecular energy, decomposition of ∼
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract As part of a research aimed at an improvement of the description of conformations of polynucleotide chains, we carried outab initio SCF-MO computations on 24 conformations of ethyl methyl phosphate (EMP), a molecule which can be taken as a model for the ω′-rotation of polynucleotides. Quantum-mechanical energies were then reproduced, with good accuracy (standard deviation of fitted fromab initio values 0.12 kcal mole−1), through a classical potential function consisting of a “6–12” Lennard-Jones plus a Coulomb term, and a contribution with twofold periodicity accounting for the anomeric effects in the phosphate group. The binding energies were analyzed using dementi's concept of Bond Energy Analysis. It was found that the variation of the binding energy as a function of conformation depends on pair atom-atom interactions distributed all over the molecule. This trend in the conformational energy is absent in the classic representation, where changes in binding energy only depend on interactions between non-bonded atom pairs alone. The dependence on interatomic distance of the quantum-mechanical energies, however, is remarkably similar to the one described by classical functions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00554385
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  • 4
    Electronic Resource
    Electronic Resource
    Spektrographische Bestimmung von Eisen, Nickel und Chrom in Platin-Netzen (1966)
    Springer
    Microchimica acta 54 (1966), S. 1162-1166 
    Details
    ISSN: 1436-5073
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Summary A method is described for the spectrographic determination of iron, nickel and chromium in platinum-rhodium nettings that are employed as catalysts in the hydrocyanic synthesis. The method is based on the dilution, with aluminium nitrate solution, of the samples dissolved in aqua regia; the diluted solution is then taken to dryness and converted to oxide. Aluminium serves as reference element.
    Abstract: Résumé On a décrit une méthode de dosage spectrographique du fer, du nickel et du chrome dans les grilles platine-rhodium utilisées comme catalyseurs dans la synthèse de l'acide cyanhydrique. Elle repose sur la dilution par une solution de nitrate d'aluminium des échantillons dissous dans l'eau régale. Ils sont ensuite séchés et utilisés sous forme d'oxydes. On prend l'aluminium comme élément de référence.
    Notes: Zusammenfassung Eine Methode zur spektrographischen Bestimmung von Eisen, Nickel und Chrom in Platin-Rhodium-Netzen, die als Katalysatoren bei der Cyanwasserstoffsynthese gebraucht werden, wurde beschrieben. Sie beruht auf der Verdünnung der in Königswasser gelösten Probe mit Aluminiumnitratlösung, die dann getrocknet und in Oxid verwandelt wird. Als Bezugselement dient Aluminium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01217723
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  • 5
    Electronic Resource
    Electronic Resource
    A quantum mechanical study of the equilibrium between 1,4- and 1,6-dialkylcyclooctatetraenes (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 248-251 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The equilibrium between three pairs of 1,4- and 1,6-dialkylcyclooctatetraenes was investigated with the two quantum mechanical algorithms, IBMOL and PCILO. PCILO computations reproduce the trend of stability within each pair of isomers obtained earlier by Allinger with molecular mechanics calculations, while IBMOL computations do not. These results not only can be explained in the light of, but also are a confirmation of Allinger's conclusions that the conformational stability is governed by the magnitude of the van der Waals' attraction between the two alkyl groups: The dispersion energy, which is essentially an electron correlation effect, is not accounted for by a method like IBMOL that, albeit ab initio, is based on the Hartree-Fock independent particle model, while it is fairly well reproduced by a method like PCILO that, albeit semiempirical, is based on a configuration interaction approach. Simulation of the full configuration interaction (CI) correction through a suitable dispersion term brings IBMOL results to a good agreement with the molecular mechanics ones.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540050307
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  • 6
    Electronic Resource
    Electronic Resource
    Graphical representation of composition and sequence distribution in copolymers (1967)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 108 (1967), S. 307-311 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1967.021080130
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  • 7
    Electronic Resource
    Electronic Resource
    The shape of calibration curves in the IR analysis of copolymer composition (1973)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 170 (1973), S. 231-234 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1973.021700118
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  • 8
    Electronic Resource
    Electronic Resource
    Derivation of the copolymerization equation from a variational principle (1975)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 176 (1975), S. 453-457 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Copolymerisationsgleichung wurde sowohl für das „terminal“- als auch für das „penultimate“-Modell unter Anwendung eines Variationsprinzips auf die Informations-entropie des Copolymeren abgeleitet.
    Notes: The copolymer composition equation for both terminal and penultimate models, was derived by applying a variational principle to the informational entropy of the copolymer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1975.021760216
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  • 9
    Electronic Resource
    Electronic Resource
    Spectroscopic method for the analysis of polyalkenamers (1973)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 11 (1973), S. 529-538 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A method based on use of NMR and infrared spectroscopy is described for the quantitative determination of the structural units generally occurring in polyalkenamers. The possibilities offered by both techniques are pointed out: in particular, the values found for the absorptivities of the infrared bands typical of unsaturated alkenamer units are extensively discussed.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1973.180110310
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  • 10
    Electronic Resource
    Electronic Resource
    A near infrared study of ethylene-propylene copolymers (1968)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 112 (1968), S. 303-306 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1968.021120128
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