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    Author(s): Frank R. Fronczek; Garret Gannuch; Wayne L. Mattice; Fred L. Tobiason; Jeff L. Broker; Richard W. Hemingway
    Date: 1984
    Source: Journal of the Chemical Society Perkin Trans II:1611-1616
    Publication Series: Miscellaneous Publication
    PDF: View PDF  (1.2 MB)

    Description

    The structure of (-)-epicatechin has been determined in the crystalline state. Crystals are orthorhombic. P212121, a=670.8(1), b=1329.1 (3), c=1426.2(4) pm, Z=4. Dc=1.516 g cm-3, R=0.041 for 1624 observations. Intramolecular hydrogen bonds are absent. The aliphatic hydroxy group and three of the four phenolic hydroxy groups participate in intermolecular hydrogen bond formation. The aromatic ring bonded to C(2) is in an equatorial position. but the hydroxy group bonded to C(3) adopts an axial position. Comparison with the published structure for 8-bromotetra-O-methyl-(+)-catechin reveals that epimerization at C(3) alters the fused ring system primarily at C(2) and C(3). The heterocyclic ring is more closely described as a half-chair in (-)-epicatechin than in 8-bromotetra-O-methyl-(+)-catechin. Dipole moments have been measured for (-)-epicatechin in solution. At 300 K the root-mean-square dipole moment is 3.91 ± 0.04 D, and the temperature coefficient is small and negative. The behaviour of the dipole moment is easily rationalized vi. a theoretical rotational isomeric state analysis based on the structure found in the crystalline state.

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    Citation

    Fronczek, Frank R.; Gannuch, Garret; Mattice, Wayne L.; Tobiason, Fred L.; Broker, Jeff L.; Hemingway, Richard W. 1984. Dipole moment, solution, and solid state structure (-)-epicatechin, a monomer unit of procyanidin polymers. Journal of the Chemical Society Perkin Trans II:1611-1616

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