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  • 1
    Electronic Resource
    Electronic Resource
    Lichtabsorptionsspektren von Carbanionen, III. Berechnungen nach dem Hückelschen LCAO-MO-Verfahren und Bandenzuordnungen (1968)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 101 (1968), S. 2785-2799 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Einfache HMO-Berechnungen ohne Berücksichtigung der Überlappungsintegrale ergeben mit der nach der Methode der kleinsten Fehlerquadrate ermittelten empirischen Beziehung ΔE = (20270 · Δm + 2520)/cm eine gute Übereinstimmung zwischen den Wellenzahlen der längstwelligen und soweit beobachtbar auch der kürzerwelligen Absorptionsmaxima der Cäsiumsalze von Carbanionen in Cyclohexylamin und den entsprechenden HMO-Übergangsenergien.  -  Bei den Carbanionen mit C2v-Symmetrie wird jeweils eine Bande großer Intensität beobachtet, wenn der berechnete Übergang in Richtung der längsten Molekülachse polarisiert ist, und eine Bande mit geringer Intensität, wenn er in der kurzen Molekülachse polarisiert ist.  -  Eine Verdrillung um die Bindung zum Carbeniat-Zentrum bei ungeraden alternierenden Carbanionen hat im Gegensatz zur experimentellen Beobachtung nach der HMO-Berechnung keine Auswirkung auf die Lage des längstwelligen Absorptionsmaximums. Eine Verdrillung um die Bindung eines p-Phenyl-Substituenten ergibt dagegen in Übereinstimmung mit dem Experiment eine hypsochrome Verschiebung.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19681010824
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  • 2
    Electronic Resource
    Electronic Resource
    Lichtabsorptionsspektren der Cäsiumsalze von Carbanionen, I. Spektroskopische Auswirkungen von Methylsubstitutionen und unterschiedlichen o.o′-Ringverbrückungen bei Carbanionen des Diphenylmethyl- und Triphenylmethyl-Typs (1968)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 101 (1968), S. 657-671 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ringmethylsubstitution bewirkt bei Carbanionen der Di- und Triphenylmethyl-Reihe eine bathochrome Verschiebung des längstwelligen Absorptionsmaximus um 3-8 mμ. Die Gesamtintensität der Bande wird dabei nicht verändert. Methylsubstitution am Carbeniat-Zentrum bewirkt bei den o.o′-verbrückten Verbindungen 9.10.10-Trimethyl-9.10-dihydroanthracenyl-(9)-cäsium (8) und 5-Methyl-10.11-dihydro-5H-dibenzo [a.d]cycloheptenyl-(5)-cäsium (9) eine bathochrome Verschiebung um 10±2 mμ, wobei als Folge einer Bandenverbreiterung die Gesamtintensität erhöht wird.Der Vergleich der Spektren von Diphenylmethyl- bzw. Di-o-tolyl-methyl-cäsium (1 bzw. 6) mit dem in seiner geometrischen Lage weitgehend fixierten 10.11-Dihydro-5H-dibenzo[a.d]cy-cloheptenyl-(5)-cäsium (4) zeigt, daß bei der unverbrückten Struktur (1 bzw. 6) die beiden Phenylringe stärker planar zum Carbeniat-Zentrum angeordnet sind als bei 4. Beim ebenfalls unverbrückten 1.1-Diphenyl-äthylhyphen;cäsium liegt dagegen eine zu 4 vergleichbar verdrillte Anordnung vor. Die Störung der Planarität des chromophoren Systems bei Carbanionen ist von einer bathochromen Verschiebung begleitet.Das Spektrum von 10.10-Dimethyl-9.10-dihydro-anthracenyl-(9)-cäsium (3b) zeigt eine Bande bei 444 mμ mit auffallend geringer Intensität, die auf eine sterische und elektronische 9.10-Wechselwirkung der geminalen Methylgruppen mit dem Carbeniat-Zentrum schließen läßt.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19681010237
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  • 3
    Electronic Resource
    Electronic Resource
    Lichtabsorptionsspektren der Cäsiumsalze von Carbanionen, II. Spektroskopische Effekte von Phenylsubstitutionen am Benzyl-Anion (1968)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 101 (1968), S. 672-680 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Phenyl-Substitution in p-Stellung (2) ergibt eine geringere Auswirkung auf die Lichtabsorption des Benzyl-Anions (1) als die Phenyl-Substitution am Carbeniat-Zentrum (3). Dies deutet auf eine unterschiedliche Störung der Planarität der π-Konjugationssysteme von 2 und 3 hin.  -  Beim Triphenylmethyl-Anion (4) sind alle drei Phenyl-Ringe trotz verdrillter Anordnung an der Lichtabsorption beteiligt, da ein charakteristisches zweibandiges Spektrum erhalten wird, das bei Ring-Verbrückung zu 5 oder 6 in das einbandige Spektrum der entsprechen-den Diphenylmethyl-Anionen übergeht. Der frei drehbare Phenyl-Rest ist daher am chromophoren System nicht mehr beteiligt. Dies ist jedoch nicht bei 5-Ring-Verbrückung zu 7 der Fall, da gegenüber dem Fluorenyl-(9)-cäsium eine neue Absorptionsbande beobachtet wird. Der Vergleich mit dem Spektrum und Modell des geometrisch fixierten Tribenzazulenyl-cäsiums 8 ergibt für die Verdrillung des 9-Phenyl-Substituenten bei 7 einen Winkel von ca. 25°.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19681010238
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  • 4
    Electronic Resource
    Electronic Resource
    Carbon acidity. 97. Cesium ion pair acidity of some sulfones in cyclohexylamineDedicated to Prof. William E. McEwen on the occasion of his seventy-fifth birthday. (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Heteroatom Chemistry 8 (1997), S. 533-537 
    Details
    ISSN: 1042-7163
    Keywords: Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The ion pair acidities of several sulfones were measured on the cesium-cyclohexylamine scale. Cyclopropyl phenyl sulfone is less acidic than isopropyl phenyl sulfone in agreement with earlier results in dimethyl sulfoxide. The acidities of a series of substituted phenyl methyl sulfones show that the sulfone group is an effective insulator; there is no significant delocalization of carbanion charge across the sulfone group into the phenyl ring. © 1997 John Wiley & Sons, Inc. Heteroatom Chem 8:533-537, 1997
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Application of various population methods to some oxygenated compounds (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 10 (1989), S. 514-519 
    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 charge on oxygen for a series of compounds was obtained using Mulliken population, natural population analysis (NPA), integrated projected electron population (IPP) analysis, and Bader's topological density analysis, “integrated Bader populations” (IBP). The orbital-based methods (Mulliken and NPA) predict oxygen charges of about -0.6 whereas the spatial-based methods (IPP and IBP) predict charges of about - 1.2 to - 1.3. The differences are ascribed primarily to the nuclear-centered basis sets used in the orbital methods that minimize local atomic polarization effects. Accordingly, such population analyses should be used for electronic structure considerations only with due circumspection. The IPP method as an approximation to IBP shows gross similarities; small but significant differences vary in a nonsystematic manner and IPP values must also be used with care.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540100409
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  • 6
    Electronic Resource
    Electronic Resource
    A study of basis set effects on structures and electronic structures of phosphine oxide and fluorophosphine oxide (1987)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 8 (1987), S. 788-793 
    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: A variety of basis sets have been used for geometric and electronic structure studies. Electronic effects were measured using integrated spatial electron populations (ISEP). The two largest basis sets used, 6-31G* and DZ+P, give significantly different results. Use of two d-orbital sets (6-31G*[dd]) or decontraction of the 2sp shell on phosphorus has little further effect. d-Orbitals on oxygen are required for consistent electronic structure results, and d-orbitals on fluorine have a small but significant effect. Use of diffuse functions, required for anions, is not recommended with small basis sets on neutral molecules. Large negative charges (≈-1.5) on oxygen are given by all of the larger basis sets by the ISEP procedure and indicate that the PO bond in these compounds is largely semi-polar. The best simple symbolic representation of phosphine oxide is H3P+—0-, rather than H3P=0.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540080606
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  • 7
    Electronic Resource
    Electronic Resource
    PRODEN: A new program for calculating integrated projected populations (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 1101-1110 
    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: Two new computational methods for the evaluation and partitioning of projected, planar, and averaged slab electron densities, implemented in the program PRODEN, are presented. The new algorithms for the projection, demarcation, and integration of electron densities are described and evaluated in terms of speed and numerical accuracy. Integrated Projected Populations are analyzed and some of the advantages and limitations of the methods are discussed.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540110914
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  • 8
    Electronic Resource
    Electronic Resource
    Die erste Kristallstruktur einer Organonatrium-Lithiumalkoxid-Verbindung - Modell einer SuperbaseDiese Arbeit wurde von der National Science Foundation (Grant CHE87-21134) gefördert. S. H. dankt der niederländischen NWO für ein Forschungsstipendium. (1993)
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 105 (1993), S. 1108-1110 
    Details
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ange.19931050727
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  • 9
    Electronic Resource
    Electronic Resource
    Direct determination of proton-exchange kinetics by 320-MHz tritium NMR spectroscopy (1991)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 29 (1991), S. 509-512 
    Details
    ISSN: 0749-1581
    Keywords: 3H NMR ; Exchange rates ; Kinetic acidity ; Kinetics ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The first application of tritium NMR spectroscopy to the direct observation of proton-exchange kinetics is described; this technique allows the study of milligram amounts of substrates and for substrates with multiple exchangeable positions. The examples include benzene and the ring and methyl positions of p-xylene reacting with cesium cyclohexylamide in cyclohexylamine, and the enolate positions of cyclohexanone and methyl 7,12-dihydroxy-3-ketocholan-24-oate reacting with heptafluorobutyric acid in dioxane.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260290517
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  • 10
    Electronic Resource
    Electronic Resource
    Integrated spatial electron populations in molecules: Application to simple molecules (1980)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 1 (1980), S. 81-87 
    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 electron projection function P(x, z) = ∫ ρ(x, y, z) dy is used to evaluate charge transfer and covalency in two series of molecules, LiX and CH3X (X = Li, BeH, BH2, CH3, NH2, OH, and F), with wavefunctions derived from STO-3G, 4-31G, and, in some cases, 6-31* ab initio calculations. The precision of the method and comparison with Mulliken populations analysis are described. Particular attention is given to CH3Li which by our criteria is wholly ionic.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540010111
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