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Report | Regular issue | Vol 23, No. 10, 1985, pp. 2709 - 2714
Published online:
DOI: 10.3987/R-1985-10-2709
The Crystal and Molecular Structure of Pelargonindin Bromide Monohydrate

Norio Saito* and Katsuhiko Ueno

*Chemical Laboratory, Meiji-Gakuin University , 1518 Kamikurata-machi, Totsuka-ku, Yokohama 244-0816, Japan

Abstract

The structure of pelargonidin, 3,5,7,4’-tetrahydroxyflavylium, bromide monohydrate, obtained by the hydrolysis of pelargonin, the major pigment of Dahlia variabilis has been determined by the X-ray method. The crystals are triclinic space group P1 with a=8.929(2), b=11.360(3), c=7.299(2)Å, α=95.00(5), β=93.61(5), γ=93.35(5)° and Z=2. The structure was solved by the heavy atom method and refined by least-squares to a final R-value of 0.057 for 2351 observed reflexions. The molecule is nearly planar. The phenyl ring makes a dihedral angle of only 3.8° with the benzopyrylium plane. The sp2-sp2 single bond connecting the benzopyrylium portion and phenyl ring is 1.458Å. The bond lengths in the benzopyrylium portion show a charasteristic feature of resonance structure. The hydroxyl groups at the 7- and 4’-positions of pelargonidin cation form hydrogen bond with Br ions. The pelargonidin molecules related by the center of symmetries are stacked along the c axis. The hydrogen bonding schemes and stacking modes of anthocyanidins so far determined are summarized.

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