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  • Wiley-Blackwell  (4)
  • 1975-1979  (4)
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  • 1
    Electronic Resource
    Electronic Resource
    Protonenresonanz-Spektroskopie ungesättigter Ringsysteme, XXI. Überbrückte [14]Annulene mit Anthracenperimeter (1975)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 108 (1975), S. 640-656 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Proton Resonance Spectroscopy of Unsaturated Ring Systems, XXI. Bridged[14]Annulenes With Anthracene PerimeterThe 1H n.m.r. spectra of bridged [14]annulenes with anthracene perimeter have been analysed. The H, H coupling constants obtained show all systems to possess a delocalised 14-π electron system. The increased shielding of the perimeter 1H resonances in α- and β-position as well as the simultanous deshielding of the bridge protons observed with increasing number of links in the bridge is attributable to geometric factors. No indications for a significant reduction of cyclic π-electron delocalisation and, as a consequence, of the diamagnetic ring current effect are found. In the case of 1, 6:8, 13-pentanediylidene-[14]annulene a conformational mobility of the bridge was detected for the first time in this series of compounds. For the assumed inversion process ΔH≠ = 13.7 kcal/mole and ΔS≠ = -0.5 e. u. were determined by lineshape analysis at different temperatures. PPP-type calculations with variable resonance integral β allow satisfactory predictions of the perimeter CC bond length, if transannular interactions of β (1, 6) = -1.1 eV for the [10]annulene and β(1,6) = β(8, 13) = -0.3 eV for the [14]annulene are considered.
    Notes: Die 1H-NMR-Spektren überbrückter [14]Annulene mit Anthracenperimeter wurden analysiert. Nach den ermittelten H, H-Kopplungskonstanten besitzen alle Systeme ein delokalisiertes 14-π-Elektronensystem. Die mit zunehmender Brückengliederzahl eintretende Abschirmung der Perimeter-1H-Resonanzen in α- und β-Position und die gleichzeitig zu beobachtende Entschirmung der Brückenprotonen kann auf geometrische Faktoren zurückgeführt werden. Für eine signifikante Beeinträchtigung der cyclischen π-Elektronendelokalisation und damit des diamagnetischen Ringstromeffekts ergeben sich keine Hinweise. Bei 1,6:8,13-Pentandiyliden-[14]annulen wird erstmals für diese Verbindungsklasse eine konformative Beweglichkeit der Brücke festgestellt. Für den angenommenen Inversionsprozeß findet man durch Linienformanalyse bei verschiedenen Temperaturen ΔH≠ = 13.7 kcal/mol und ΔS≠ = -0.5 Clausius. PPP-Rechnungen mit variablem Resonanzintegral β gestatten eine gute Vorhersage der Perimeter-CC-Bindungslängen, wenn für die transannulare Wechselwirkung β (1,6) = -1.1 eV im [10]Annulen und β (1,6) = β (8,13) = -0.3 eV im [14]Annulen angenommen wird.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19751080230
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  • 2
    Electronic Resource
    Electronic Resource
    Protonenresonanz-Spektroskopie ungesättigter Ringsysteme, XXVII. Der Benzolkern als Sonde für die π-Elektronenstruktur von Annulenen; Teil IV: Dehydrobenzoannulene (1979)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 112 (1979), S. 71-83 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Proton Resonance Spectroscopy of Unsaturated Ring Systems, XXVII. The Benzene Nucleus as a Probe for the π-Electronic Structure of Annulenes; Part IV: DehydrobenzoannulenesThe 1H NMR Spectra of 6,9-dimethyl-7-monodehydrobenzo[12]annulene (1), 7,9-bisdehydrobenzo[14]annulene (2a), 6,11-dimethyl-7,9-bisdehydrobenzo[14]annulene (2a), 6,11-dimethyl-7,9-bisdehydrobenzo[16]annulene (3), and 9,11-bisdehydrobenzo[18]annulene (4) have been analyzed with respect to chemical shifts and H,H coupling constants. The electronic ground state properties of the annulene rings have been investigated using the Q-value method2). On the basis of the chemical shifts it was found that, compared to the free bisdehydroannulenes, the diatropic behaviour of 2a and 4 is reduced by ca. 70-80%, whereas the paratropic nature of 3 is diminished by less than 50%. Strong π-bond fixation exists in the annulene rings of 1-4.The conformations of the systems are discussed.
    Notes: Die 1H-NMR-Spektren von 6,9-Dimethyl-7-monodehydrobenzo[12]annulen (1), 7,9-Bisdehydrobenzo[14]annulen (2), 6,11-Dimethyl-7,9-bisdehydrobenzo[14]annulen (2a), 6,11-Dimethyl-7,9-bisdehydrobenzo[16]annulen (3) und 9,11-Bisdehydrobenzo[18]annulen (4) wurden hinsichtlich chemischer Verschiebungen und H,H-Kopplungskonstanten analysiert. Die elektronischen Eigenschaften des Grundzustandes der Annulenringe wurden mit Hilfe der Q-Wert-Methode2) untersucht. Aus den chemischen Verschiebungen wurde abgeleitet, daß das diatrope verhalten von 2a und 4 im Vergleich zu dem der freien Bisdehydroannulene um ca. 70-80% reduziert ist, während das paratrope Verhalten von 3 um weniger als 50% abgenommen hat. In den Annulenringen von 1-4 liegt eine starke π-Bindungsfixierung vor. Die Konformationen der Systeme werden diskutiert.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19791120107
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  • 3
    Electronic Resource
    Electronic Resource
    Protonenresonanz-Spektroskopie ungesättigter Ringsysteme, XXVI.Der Benzolkern als Sonde für die π-Elektronenstruktur von Annulenen; Teil III: Dibenzoannulene und Dibenzoannulen-Ionen (1978)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1978 (1978), S. 165-175 
    Details
    ISSN: 0075-4617
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Proton Resonance Spectroscopy of Unsaturated Ring Systems, XXVI1).  -  The Benzene Nucleus as a Probe for the π-Electronic Structure of Annulenes; Part III: Dibenzoannulenes and Dibenzoannulene IonsThe Q-value method for the classification of cyclic π-systems [D. Cremer and H. Günther, Liebigs Ann. Chem. 763, 87 (1972)] is applied to dibenzoannulenes and dibenzoannuleneions. For this purpose the 1H NMR spectra of 1,2,5,6-dibenzocycloocta-1,5-diene-3,7-diyne (1), 1,2,5,6-dibenzocyclooctenediide (5) 1,2,3,4-dibenzocyclooctene (6), and 1,2,3,4-dibenzocyclooctenediide (7) have been completely analyzed. Antiaromatic (4n) character is found for 1. The problems associated with the interpretation of proton resonance frequencies in dehydroannulenes are discussed.
    Notes: Die Q-Wert-Methode zur Klassifizierung cyclischer π-Systeme [D. Cremer und H. Günther, Liebigs Ann. Chem. 763, 87 (1972)] wird auf Dibenzoannulene und Dibenzoannulen-Ionen angewandt. Dazu wurden die 1H-NMR-Spektren von 1,2,5,6-Dibenzocycloocta-1,5-dien-3,7-diin (1), 1,2,5,6-Dibenzocyclooctendiid (5), 1,2,3,4-Dibenzocycloocten (6) und 1,2,3,4-Dibenzocyclooctendiid (7) komplett analysiert. Für 1 wurde antiaromatischer (4n) Charakter gefunden. Die Problematik der Interpretation von Protonenresonanzfrequenzen bei Dehydroannulenen wird diskutiert.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.197819780119
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  • 4
    Electronic Resource
    Electronic Resource
    3J(HH)—Pμ,ν correlation for planar 7-membered cyclic π-systems - structural effects on 3J(HH)Proton Magnetic Resonance Spectra of Unsaturated Ring Systems, Part XXIV; for Part XXIII see Ref. 47. (1977)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 9 (1977), S. 420-425 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It is shown that sterically unperturbed vicinal HH coupling constants in planar 7-membered π-systems correlate linearly with the HMO π-bond order: 3J(HH) = 20.91Pμ,ν-3.85 (r.m.s. error 0.26 Hz, correlation coefficient =0.988). Systematic deviations from this relationship which most probably originate from valence angle changes are found for fused π-systems containing rings of different size. Model calculations using the CNDO/2 method as well as finite perturbation theory and INDO wave functions support the experimental findings. An improvement of existing 3J(HH)—Pμ,ν correlations for planar 6-membered rings is possible if CNDO/2 π-bond orders are used instead of HMO or PPP-SCF data.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270090711
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