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  • 1
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    The electronic structure of polyenes and unsaturated carbonyl compounds (1978)
    Elsevier
    Details
    Publication Date: 1978-01-01
    Print ISSN: 0040-4020
    Electronic ISSN: 1464-5416
    Topics: Chemistry and Pharmacology
    Published by Elsevier
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    PAPER CURRENT
  • 2
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    Conjugative interaction between cyclopropyl walsh orbitals and π-orbitals in dispiro[2.2.2.2]deca-4,9-diene (1975)
    Elsevier
    Details
    Publication Date: 1975-01-01
    Print ISSN: 0040-4039
    Electronic ISSN: 1873-3581
    Topics: Chemistry and Pharmacology
    Published by Elsevier
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    PAPER CURRENT
  • 3
    Electronic Resource
    Electronic Resource
    VB calculations with orthogonal basis functions (1978)
    Springer
    Theoretical chemistry accounts 47 (1978), S. 193-203 
    Details
    ISSN: 1432-2234
    Keywords: VB method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract As a first step in the development of a semiempirical VB method,ab initio VB calculations were performed to obtain potential energy curves for the molecules HF and BeH2 and the energy profile of the collinear exchange reaction F + H2 → HF + H. The applicability of the method is discussed with particular emphasis on the calculation of integrals over OAO's, the choice of valence structures to be included in the CI scheme and the interpretation of the wave function in terms of OAO's.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00577161
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  • 4
    Electronic Resource
    Electronic Resource
    Molecular orbital calculations based on linear combinations of fragment orbitals (1978)
    Springer
    Theoretical chemistry accounts 49 (1978), S. 77-92 
    Details
    ISSN: 1432-2234
    Keywords: Photoelectron spectra, interpretation of ∼
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A semiempirical MO method based on localized fragment orbitals has been developed, which is particularly suited for the construction of orbital correlation diagrams for the discussion of the electronic structure of complex molecules in terms of fragments and their interactions. The method allows for the inclusion of experimental ionization potentials and electron affinities of the fragments within the calculation of the Fock matrix elements and may thus form the basis of an interpretation of photoelectron spectra, comparable to the interpretation of UV spectra by means of the MIM method of Longuet-Higgins and Murrell. Several levels of approximation are discussed using the acrolein molecule as an example.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00552740
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  • 5
    Electronic Resource
    Electronic Resource
    Photoelektronenspektren organischer Verbindungen, VIII. 7,8-Dimethylenbicyclo[2.2.2]octa-2,5-dien und verwandte Verbindungen (1975)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 108 (1975), S. 2923-2933 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Photoelectron Spectra of Organic Compounds, VIII. 7,8-Dimethylenebicyclo[2.2.2]octa-2,5-diene and Related CompoundsThe photoelectron spectra of vicinal dimethylene derivatives of cyclohexane and cyclohexene bridged by a group with π-, Walsh, or n-orbitals (3-13) are discussed on the basis of a LCMO model within the HMO approximation. The homoconjugative interaction between the semicyclic diene and one other group is only slight; more pronounced effects are observed if an interaction with two other groups is possible, as in the case of 7,8-dimethylenebicyclo[2.2.2]octa-2,5-diene (3) or 5,6-dimethylene-7-oxabicyclo[2.2.1]hept-2-ene (12).
    Notes: Die Photoelektronenspektren von vicinalen Dimethylenderivaten des Cyclohexans und Cyclohexens, die durch eine Gruppe mit π-, Walsh- oder n-Orbitalen überbrückt sind (3-13), werden auf der Grundlage eines LCMO-Modells im Rahmen der HMO-Näherung diskutiert. Die homokonjugative Wechselwirkung zwischen dem semicyclischen Diensystem und einer weiteren Gruppe ist gering; ausgeprägtere Effekte treten auf, wenn wie im Falle des 7,8-Dimethylenbicyclo-[2.2.2]octa-2,5-diens (3) oder des 5,6-Dimethylen-7-oxabicyclo[2.2.1]hept-2-ens (12) eine Wechselwirkung mit zwei weiteren Gruppen möglich ist.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19751080912
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  • 6
    Electronic Resource
    Electronic Resource
    Struktur und innere Beweglichkeit sterisch fixierter s-cis-Butadiene (1979)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 112 (1979), S. 890-898 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Structure and Internal Flexibility of Sterically Fixed s-cis-ButadienesForce Field Calculations yield a coplanar arrangement of the π systems of the vicinal exo-methylene derivatives 1 and 2 of cyclobutane and cyclopentane and of the corresponding derivatives 4-7 of norbornane, bicyclooctane, bicyclononane and bicyclooctene. The detailed geometry of the cis-butadiene unit is essentially determined by the ring system. For the cyclohexane derivative 3 on the other hand a chair conformation is obtained. 2,5 and 6 are rather flexible molecules for which torsions of the π system up to 20° require energies less than 5 kJ/mol, whereas for the more rigid systems 1, 4 and 7 approximately 10 kJ/mol are necessary for twisting the π system by 10°.
    Notes: Kraftfeldrechnungen ergeben für die vicinalen exo-Methylenderivate 1 und 2 des Cyclobutans und des Cyclopentans sowie für die entsprechenden Derivate 4-7 des Norbornans, Bicyclooctans, Bicyclononans und des Bicyclooctens eine planare Anordnung des π-Systems. Dessen genaue Geometrie im wesentlichen durch das cyclische Gerüst bestimmt wird. Das Cyclohexanderivat 3 dagegen liegt in einer Sesselform vor. Die Moleküle 2, 5 und 6 zeichnen sich durch große Flexibilität aus, Torsionen des π-Systems bis etwa 20° erfordern Energien von weniger als 5 kJ/mol, während für die starreren Systeme 1,4 und 7 bereits bei Verdrillungen um 10° etwa 10 kJ/mol erforderlich sind.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19791120314
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  • 7
    Electronic Resource
    Electronic Resource
    Konjugative Wechselwirkungen des Cyclobutans (1978)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 111 (1978), S. 944-957 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Conjugative Interactions of Cyclobutane1,1,3,3-Tetramethyl-2-vinyl- (3), 3-ethynyl-1,1-dimethyl- (5), and 2-ethynyl-1,1,3,3-tetramethyl-cyclobutane (6) were synthesized in order to analyze the conjugative properties of cyclobutane. From the PE spectra of these compounds as well as of related model compounds an interaction term HRS = -0.54 eV to describe the conjugation between cyclobutane and a π system was obtained within the frame work of a LCBO model. From the spectra of the ethynyl-substituted cyclobutanes 4-6 it is seen that in contrast with the findings for the corresponding cyclopropyl compounds this conjugative interaction does not depend on the conformation. By means of methyl substitution which lowers the energy difference between cyclobutane and π orbitals, the conjugative power of the cyclobutane ring may be enhanced considerably. Without this effect which is particularly effective for the position α relative to the π system, the influence of the cyclobutane on the π system hardly exceeds that of an alkyl substituent of comparable size.
    Notes: Zur Analyse der konjugativen Eigenschaften des Cyclobutans wurden 1,1,3,3-Tetramethyl-2-vinyl- (3), 3-Ethinyl-1,1-dimethyl- (5) und 2-Ethinyl-1,1,3,3-tetramethylcyclobutan (6) synthetisiert. Aus den Photoelektronenspektren der vinylsubstituierten Cyclobutane und Vergleichs-verbindungen läßt sich eine Wechselwirkung HRS = -0.54 eV ableiten, die im Rahmen eines LCBO-Modells die Konjugation zwischen Cyclobutan und π-System beschreibt. Diese Konjugation ist im Unterschied zu Cyclopropylderivaten nicht konformationsabhängig, wie die Spektren der ethinylsubstituierten Cyclobutane 4-6 zeigen. Die Konjugationsfähigkeit des Cyclobutans läßt sich durch Methylsubstitution, welche die Energiedifferenz zwischen Ring- und π-Orbitalen vermindert, beträchtlich steigern. Ohne diesen Effekt, der in α-Stellung zum π-Substituenten besonders wirksam ist, übersteigt der Einfluß des Cyclobutans auf π-Systeme kaum den Einfluß vergleichbar großer Alkylsubstituenten.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19781110316
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  • 8
    Electronic Resource
    Electronic Resource
    Elektronenstruktur von Alkyl-aryl- und Alkyl-vinyl-ethern (1979)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 112 (1979), S. 1614-1625 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Electronic Structure of Alkyl Aryl and Alkyl Vinyl EthersFor the evaluation of the interactions between π electrons of the CC double bond and lone Pairs at the 0 atom of α, β-unsaturated ethers p. e. spectra of some alkyl aryl ethers 1-3 were recorded and compared with those of alkyl vinyl ethers 5. The data could be interpreted by means of orbital correlation diagrams provided the interaction with energetically high-lying σ orbitals of the correct symmetry was taken into account. Sterically hindered alkyl aryl ethers were found to exist in a perpendicular conformation; in sterically unhindered ethers like anisole a less stable isomer having this conformation was detected. In the case of alkyl vinyl ethers non-bonding interactions favour the s-cis conformation, whereas sterically hindered molecules of this type prefer the s-trans form. From p. e. spectra at higher temperatures (up to 510 K) the relative conformational energies are estimated. The results of the p. e. analysis are used for the interpretation of some reactions of α,β-unsaturated ethers.
    Notes: Um das Ausmaß der Konjugation zwischen π-Elektronen der CC-Doppelbindung und freien Elektronenpaaren am O-Atom α, β-ungesättigter Ether zu ermitteln, wurden die Photoelektronenspektren einer Anzahl von Alkyl-aryl-ethern 1-3 aufgenommen und mit den Spektren von Alkyl-vinyl-ethern 5 verglichen. Die Ergebnisse lassen sich mit Hilfe von Orbitalkorrelationsdiagrammen vollständing interpretieren, sofern man energetisch hochliegende σ-Orbitale geeigneter Symmetrie in die Betrachtung einbezieht. Sterisch gehinderte Alkyl-aryl-ether nehmen eine perpendikuläre Konformation ein, die bei sterisch nicht gehinderten Verbindungen wie etwa Anisol als zweite weniger stabile Form gefunden wird. Im Fall der Alkyl-vinyl-ether überwiegt aufgrund einer nichtbindenden Wechselwirkung die s-cis-Konformation bei sterisch nicht gehinderten Ethern, während sonst die s-trans-Konformation bevorzugt wird. Durch die Aufnahme von Photoelektronenspektren bei Temperaturen bis 510 k lassen sich die Energieunterschiede zwischen den verschiedenen Konformeren abschätzen. Die Ergebnisse der PE-Untersuchungen Können zur Interpretation von Reaktionen α,β-ungesättigter Ether herangezogen werden.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19791120512
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  • 9
    Electronic Resource
    Electronic Resource
    13C—13C coupling constants of cyclobutane derivatives (1979)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 12 (1979), S. 107-108 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Five 13C-labelled cyclobutane derivatives were synthesized and the couplings involving the labelled carbon were determined.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270120215
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  • 10
    Electronic Resource
    Electronic Resource
    Konstitution und Lichtabsorption organischer Farbstoffe (1978)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 12 (1978), S. 1-11 
    Details
    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ciuz.19780120102
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