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Conformation of the ground-state dimer in poly(ethylene terephthalate) (1993)

Dodge, Robert W. ; Mattice, Wayne L.

Bognor Regis [u.a.] : Wiley-Blackwell

Journal of Polymer Science Part B: Polymer Physics 31 (1993), S. 207-212

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ISSN: 0887-6266

Schlagwort(e): dimer ; fluorescence ; PET ; poly(ethylene terephthalate) ; Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Physik

Notizen: Absorbance, excitation, and emission measurements have been performed with methyl benzoate and five model compounds, C6H5COO (CH2)xOOCC6H5, x = 2-6. Under appropriate conditions, three of the model compounds (those with x = 3, 4, 5) show evidence for the formation of intramolecular ground-state dimers. The model compound with x = 5 can form two types of dimers which emit with different energies. The model compound with x = 3 forms one of these dimers, and the model compound with x = 4 prefers the other ground-state dimer. Molecular modeling of the dimers suggests that the two conformations of the ground-state dimers differ in the orientation of the two C=O bonds. In the one dimer these two bonds are nearly parallel, but in the other they make an angle of about 120°. © 1993 John Wiley & Sons, Inc.

Zusätzliches Material: 7 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/polb.1993.090310209

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Digitale Medien

Conformational analysis of oligomeric flavanoids. 2For Part 1, see Ref. 8. - methyl ether acetate derivatives of profisetinidins (1995)

Steynberg, Jan P. ; Brandt, E. Vincent ; Ferreira, Daneel ; [weitere]

Chichester : Wiley-Blackwell

Organic Magnetic Resonance 33 (1995), S. 611-620

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ISSN: 0749-1581

Schlagwort(e): NMR ; 1H NMR ; condensed tannins ; profisetinidins ; stereochemistry ; conformation ; rotational isomers ; Chemistry ; Analytical Chemistry and Spectroscopy

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The profisetinidins are the most important polyflavanoids of commerce, making up the major constituents of wattle and quebracho tannins. Even within the dimeric profisetinidins, substantial complexity exists because of stereo-, regio-, rotational and conformational isomers. Definition of the stereochemistry of the upper and lower flavan units, the location of the interflavanoid bond, the conformation of the heterocyclic rings in the upper and lower flavan units and the conformations of major and minor rotational isomers in a series of methyl ether acetate derivatives of dimeric profisetinidin diastereomers is possible by application of COSY and NOE experiments. All compounds studied were present in two rotameric forms with the more compact conformation favored. The heterocyclic ring in the upper chain extender unit was predominantly in an E-conformation (i.e. half-chair in 2R,3S isomers and a ‘reverse’ half-chair in the 2S,3R isomers). The heterocyclic ring conformation of the terminal cate-chin unit, although mostly in an E-conformation, was often represented by significant proportions of A-conformers.

Zusätzliches Material: 8 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/mrc.1260330802

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