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  • 1
    Electronic Resource
    Electronic Resource
    PE-spectroscopic investigation of nonconjugated π,π interactions in (seco)dodecahedradienes  -  on the route to an experimental ethylene/ethylene cycloaddition reaction coordinate (1995)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1995 (1995), S. 2019-2025 
    Details
    ISSN: 0947-3440
    Keywords: (Seco)dodecahedradienes ; PE spectroscopy ; π,π Interaction, nonconjugated, through-space, through-bond ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Nature and extent of nonconjugated π,π interactions in (bis)-secododecahedradienes and (pentagonal, non-pentagonal) dodecahedradienes with transannular π,π distances ranging from ca. 2.8 to ca. 3.5 Å - representing well defined points on the D2h [π2 + π2] reaction coordinate - were studied by PE spectroscopy. The π,π splitting of 0.68 eV measured at the largest π,π distance of ca. 3.5 Å (1,16-dodecahedradiene 3a) was attributed to ca. 50% each of through-space and through-bond conjugation (analysis of precanonical MOs).
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.1995199511283
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  • 2
    Electronic Resource
    Electronic Resource
    Vinylogous β-Carotenes: Generation, Storage, and Delocalization of Charge in Carotenoids (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 2205-2213 
    Details
    ISSN: 0947-3440
    Keywords: Carotenoids ; C26—C70 β-carotenes ; Cyclic voltammetry ; Photoelectron spectroscopy ; Semiempirical calculations ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In this paper, we report on the synthesis of β-carotenes of variable chain length with between 5 and 23 double bonds (1-7). These oligoenes were prepared by McMurry and Wittig reactions. The tetradecapreno-β-carotene 7 would seem to be the longest β-carotene yet reported. Furthermore, we investigated the electronic properties using cyclic voltammetry and photoelectron spectroscopy (UPS) to generate open-shell and closed-shell ions of carotenoids in solution and in the solid state, respectively. With increasing chain length (≥ 11 double bonds), even the generation of tetracations and tetraanions could be observed by cyclic voltammetry. Extending the number of conjugated bonds causes the potentials to converge to limiting values. All electron-transfer processes occur in one-electron steps, which are close to each other in pairs. The potential difference between the first oxidation potential and the first reduction potential is a linear function of the reciprocal chain length. Despite the different techniques used (CV and UPS) and the different condensed phases, there is an excellent correspondence between the energies of the radical cation states generated by the two methods. This shows that the radical cation formation is principally determined by the chain length. The structures of the ion states were investigated using semiempirical methods at the NDDO level. Charge delocalization and bond relaxation are not identical and do not utilize the same number or the same kind of atoms. It can be shown that from the length of 20 double bonds onwards, the effective conjugation length for doubly-charged cations converges slowly to a limiting value.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719971106
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  • 3
    Electronic Resource
    Electronic Resource
    Notiz über die hoch stereoselektive 1,2-Wasserstoffverschiebung in einem Bishomonorbornadien (1974)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 107 (1974), S. 1403-1405 
    Details
    ISSN: 0009-2940
    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/cber.19741070438
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  • 4
    Electronic Resource
    Electronic Resource
    Notiz über eine beobachtete through-bond-Wechselwirkung über vier σ-Bindungen (1974)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 107 (1974), S. 3143-3145 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic 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/cber.19741070935
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  • 5
    Electronic Resource
    Electronic Resource
    Vertikale oder nicht-vertikale Stabilisierung im Pentacyclo[4.3.0.02,4.03,8.05,7]non-9-yl-Kation? Das 9-Methylenpentacyclononan-Radikalkation (1977)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 110 (1977), S. 3010-3019 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Vertical or Nonvertical Stabilization in the 9-Pentacyclo[4.3.0.02,4.03,8.05,7]nonyl Cation? The 9-Methylenepentacyclononane Radical Cation1)A photoelectron spectroscopic investigation of the radical cation of methylenehomocuneane 8, together with the sterically rigid bicyclopropyls 5, 6, 7 and 9, reveals a vertical stabilization of comparable order (β ≈ —0.3 eV) in the radical cations of 5 and 8. The differences in solvolysis rate enhancements of 17/18 (a factor of 20) and 3/1 (a factor of 10(12) therefore cannot be accounted for by vertical stabilization effects but demonstrate impressively the homoaromatic stabilization in a distorted bridged transition state on the reaction coordinate between 3 and 4.
    Notes: Durch eine photoelektronenspektroskopische Untersuchung des Radikalkations des Methylenhomocuneans 8 in Verbindung mit den sterisch fixierten Bicyclopropylen 5, 6, 7 und 9 wird gezeigt, daß die vertikale Stabilisierung in den Radikalionen von 5 und 8 von vergleichbarer Größenordnung ist (β ≈ —0.3 eV). Der Unterschied in den Solvolysebeschleunigungen 17/18 (Faktor 20) und 3/1 (Faktor 10(12)) kann deshalb nicht auf vertikale Stabilisierungseffekte zurückgeführt werden, sondern demonstriert eindringlich die homoaromatische Stabilisierung in einem verzerrten, überbrückten Übergangszustand auf der Reaktionskoordinate zwischen 3 und 4.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19771100906
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  • 6
    Electronic Resource
    Electronic Resource
    Photoelektronenspektroskopische Untersuchung transanularer π-, σ- und n-Wechselwirkungen in brückenkopfsubstituierten Triptycenen (1983)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 116 (1983), S. 2546-2553 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Photoelectron Spectroscopic Investigation of Transanular π-, σ-, and n-Interactions in Bridgehead Substituted TriptycenesTwo kinds of intramolecular interactions are observed in triptycenes (1, 3, 4) by PE-spectroscopy. The longicyclic π,π-homoconjugation turns out to be of similar magnitude as in cyclophanes. The longitudinal coupling of bridgehead substituents by means of suitable σ-bonds of the bicyclo [2.2.2]octane skeleton amounts to about 0.25 eV in the 9,10-dibromotriptycene 4.
    Notes: Im Triptycen-System (1, 3, 4) werden photoelektronenspektroskopisch zwei Arten intramolekularer Wechselwirkungen beobachtet. Die longicyclische π,π-Homokonjugation ist von ähnlicher Größe wie in Cyclophanen. Die longitudinate Kopplung von Brückenkopfsubstituenten mittels geeigneter σ-Bindungen des Bicyclo[2.2.2]octan-Gerüstes wird im 9,10-Dibromderivat 4 zu 0.25 eV abgeschätzt.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19831160713
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  • 7
    Electronic Resource
    Electronic Resource
    PE- und 13C-NMR-spektroskopische Untersuchungen zur Homokonjugation in 7-Alkylidennorbornadienen (1985)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 118 (1985), S. 2514-2543 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: PE and 13C NMR Spectroscopical Investigations of the Homoconjugation in 7-AlkylidenenorbornadienesThe PE and 13C NMR spectra of the norbornadienes 2a - n and norbornanes 3a - n have been measured and analyzed. In the case of 2 the homoconjugation depends essentially upon the size of the coefficient at C-7 which is determined by the substituents at C-8. The homoconjugation is described by the experimental parameter Heff that correlates significantly against the π-polarization of the semicyclic double bond. There is no simple relationship between Heff and ΔΔδ(13C); the difference of the total atomic charge ΔΔq7,8, however, contributes to ΔΔδ(13C).
    Notes: Die Photoelektronen- und 13C-NMR-Spektren der Norbornadiene 2a - n sowie der Norbornane 3a - n wurden gemessen und analysiert. In 2 ist der Fall verwirklicht, bei dem die Homokonjugation im wesentlichen nur von der Größe des Koeffizienten an C-7 abhängt, der seinerseits von den Substituenten an C-8 bestimmt wird. Der Parameter Heff, der die Homokonjugation experimentell beschreibt, korreliert signifikant mit der π-Polarisation der semicyclischen Doppelbindung. Zwischen Heff und ΔΔδ(13C) besteht kein einfacher Zusammenhang; jedoch leistet die Differenz der totalen Atomladung ΔΔq7,8 einen Beitrag zu ΔΔδ(13C).
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19851180627
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  • 8
    Electronic Resource
    Electronic Resource
    π-Orbital-Wechselwirkungen „through space“ und „through bond“ in Tricyclo[4.2.0.0]octadienen (1973)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 106 (1973), S. 28-34 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: π-Orbital Interaction „Through Space“ and „Through Bond“ in Tricyclo[4.2.0.02,5]octadienesThe first four bands in the photoelectron spectra of anti- and syn-tricyclo[4.2.0.02,5]octadiene (2 and 3, respectively) have been assigned to specific molecular orbitals. This assignment is based on the concept of „through space“ and „through bond“( interaction between the two basis π-orbitals. Because of the different configurations of 2 and 3 it is possible to separate the two types of interactions. In both cases the „through bond“ interaction dominates. As a result the symmetric linear combination π+ (symmetric with respect to the twofold rotation axis in 2 or the plane of symmetry in 3) lies above the antisymmetric combination π-. The orbital energy differences ε(π+) - ε(π-) are 0.97 eV in 2 and 0.36 eV in 3.
    Notes: Die vier ersten Banden im Photoelektronenspektrum des anti- und des syn-Tricyclo[4.2.0.02.5]-octadiens (2 bzw. 3) werden, unter Verwendung des Konzepts der „through space“- und „through bond“-Wechselwirkung zwischen den beiden Basis-π-Orbitalen, bestimmten Molekülorbitalen zugeordnet. Wegen der unterschiedlichen Konfiguration von 2 und 3 lassen sich im vorliegenden Fall die beiden Wechselwirkungstypen trennen. Sowohl in 2 als auch überraschenderweise in 3 dominiert die „through bond“-Wechselwirkung, so daß in beiden Fällen die symmetrische Linearkombination π+ der π+-Orbitale (in 2 bezüglich der zweizähligen Achse, in 3 bezüglich der Spiegelebene) energetisch über der antisymmetrischen Kombination π- zu liegen kommt. Die Energiedifferenz ε(π+) - ε(π-) beträgt in 2 0.97 eV, in 3 0.36 eV.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19731060105
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  • 9
    Electronic Resource
    Electronic Resource
    Eine neue Synthese für Tetracyclo[3.3.0.02,8.04,6]octan-3-one durch intramolekulare [2π + 2 σ]-Thermocycloaddition (1974)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 107 (1974), S. 680-685 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: A New Synthesis of Tetracyclo[3.3.0.02.8.04.6]octan-3-ones by Intramolecular Thermal [2π + 2σ]-CycloadditionThe synthesis of the tetracyclooctanone 19 by thermolysis of the tricyclic acetal 15 and subsequent removal of the acetal group is described. Thus, a third synthetic access to this system is now available. The reaction involves the cycloaddition of a thermally ring-opened cyclopropane to a double bond.
    Notes: Die Synthese des Tetracyclooctanons 19 durch Thermolyse des tricyclischen Acetals 15 und anschließende Entacetalisierung wird beschrieben. Damit bietet sich ein dritter synthetischer Zugang zu diesem System an. Die Reaktion beinhaltet die Cycloaddition eines thermisch ringgeöffneten Cyclopropans an eine Doppelbindung.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19741070240
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  • 10
    Electronic Resource
    Electronic Resource
    Transanulare Wechselwirkung des Azo-Chromophors in isodrinanalogen Systemen1) (1981)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 423-432 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Transanular Interactions of the Azo Chromophore in Isodrin-type Systems1)The unusual transanular photoreactivity of the azo-compound 5 is also reflected in its photoelectron spectrum. The investigation of compounds 5, 13 and 14 reveals an effective interaction in 5 (through-bond and through-space) with H ij = -0.62 eV between πNN and πCC. This experimental value fits in well with known parameters of analogous isodrin-type systems. The excited states are looked into by means of semiempirical calculations with model compounds 17 and 19. Both the n-π+* and (at shorter wavelength) the π-π+* transition are conducive to an intramolecular photocycloaddition. X-ray diffraction has been used to determine the πNN,πCC-transanular distance (2.91Å).
    Notes: Die ungewöhnliche transanulare Photoreaktivität der Azoverbindung 5 spiegelt sich auch im Photoelektronenspektrum wider. Die Untersuchung der Verbindungen 5, 13 und 14 läßt eine effektive Wechselwirkung (through-bond und through-space) von Hij = -0.62 eV zwischen πNN und πNN in 5 erkennen. Dieser experimentelle Wert steht in ausgezeichneter Übereinstimmung mit bekannten Parametern analoger isodrinartiger Systeme. An den Modellverbindungen 17 und 19 werden die angeregten Zustände mit Hilfe semiempirischer Rechnungen untersucht. Sowohl der n-;π+* - als auch der kurzwellige π-π+* Übergang sind einer intramolekularen Photocycloaddition förderlich. Durch Röntgenbeugung wird der πNN, πCC-Transanularabstand zu 2.91 Å ermittelt.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19811140203
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