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  • Chemistry  (3)
  • 1
    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 chirooptischen Eigenschaften von stereoregulären Polymeren aus optisch aktivem 4-Phenyl-1-hexen (1) und 5-Phenyl-1-hepten (2) sowie von Copolymeren aus 1 und 4-Methyl-1-penten (3) wurden untersucht. Der Vergleich des Drehwerts sowie der CD-Spektren im Bereich der π→π*-Absorptionsbanden des aromatischen Chromophors dieser Polymeren mit den entsprechenden Eigenschaften der optisch aktiven Phenylalkane erlaubt den Schluß, daß die Makromoleküle von Homopolymeren aus 1 und von Copolymeren aus 1 und 3 Segmente enthalten, die in Helixform mit vorherrschendem Drehsinn vorliegen. Kein Beweis für das Vorliegen dieses Typs wurde im Fall der Polymeren aus 2 erhalten. Die Konformationsanalyse von Molekülmodellen zeigt, daß Rechtshelices in den Polymeren aus 1 mit absoluter R-Konfiguration bevorzugt sind, wie beim Poly[(R)-4-methyl-1-hexen] gefunden wurde. Die Beziehungen zwischen der Konformation der Makromoleküle und den CD-Kurven im Bereich von 275-185 nm sind im Einklang mit frühern Ergebnissen, die im Fall von Copolymeren aus Styrol mit optisch aktiven α-Olefinen erhalten wurden.
    Notes: The chiroptical properties of stereoregular polymers of optically active 4-phenyl-1-hexene (1) and 5-phenyl-1-heptene (2) as well as of the copolymers of 1 with 4-methyl-1-pentene (3) were investigated. The comparison of the rotatory power and of the CD spectra in the spectral region of the π→π* electronic transitions of the aromatic chromophore of these polymers with the corresponding properties of optically active phenylalkanes allows the conclusion that the macromolecules of the homopolymer of 1 as well as of its copolymer with 3 contain chain blocks in helical conformation with a predominant direction of the screw. No evidence of this type was obtained for the polymers from 2. Conformational analysis based on molecular models shows that in the case of 1 having R absolute configuration, the favoured direction of the screw is the right handed one as found for poly[(R)-4-methyl-1-hexene]. The relationships between the conformation of the macromolecules and CD of the phenyl chromophore between 275 and 185 nm are consistent with previous results concerning copolymers of styrene with optically active α-olefins.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1434-193X
    Keywords: Cyclodextrins ; NMR spectroscopy ; Chiral solvating agent ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Benzoylated and benzylated cyclodextrins give rise to non-equivalence in the 1H-NMR spectra of racemates of 3,5-dinitrophenyl derivatives of chiral amines, amino alcohols, alcohols, carboxylic acids and amino acids in CDCl3 solution, suggesting their potential use as CDCl3-soluble cyclodextrinic chiral solvating agents (CSAs) in NMR spectroscopy. Cyclodextrins bearing aromatic substituents at the primary or secondary sites only are more efficient CSAs compared to exhaustively substituted ones. NMR investigations based on NOE measurements or complexation shift determinations strongly suggest non-inclusive interaction mechanisms for these selector/selectand systems.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1434-193X
    Keywords: Cyclodextrins ; NMR spectroscopy ; NOE ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The conformational features of alkylated, benzoylated, and benzylated cyclodextrins in solution were analysed by NOE and proton-selective relaxation methods and were compared to those of native compounds.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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