Browsing by Author "Lemmerer, Andreas"

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    Chiral carboxylic acids and their effects on melting-point behaviour in co-crystals with isonicotinamide
    (2008) Lemmerer, Andreas; Ba´thori, Nikoletta B; Bourne, Susan A
    The crystal structures of co-crystals of two systems of chiral carboxylic acids, optically active and racemic 2-phenylpropionic acid and 2-phenylbutyric acid, with isonicotinamide are reported to investigate the effects of the chirality of the chiral carboxylic acids on the melting point of the co-crystal complexes. It was found that the racemic co-crystal has a higher melting point than the optically active co-crystal, which correlates with the denser packing arrangement inherent in centrosymmetric space groups.
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    The hydrogen-bonding patterns of 3-phenylpropylammonium benzoate and 3-phenylpropylammonium 3-iodobenzoate: generation of chiral crystals from achiral molecules
    (2008) Lemmerer, Andreas
    The crystal structures and hydrogen-bonding patterns of 3-phenyl­propyl­ammonium benzoate, C9H14N+·C7H5O2-, (I), and 3-phenyl­propyl­ammonium 3-iodo­benzoate, C9H14N+·C7H4IO2-, (II), are reported and compared. The addition of the I atom on the anion in (II) produces a different hydrogen-bonding pattern to that of (I). In addition, the supra­molecular heterosynthon of (II) produces a chiral crystal packing not observed in (I). Compound (I) packs in a centrosymmetric fashion and forms achiral one-dimensional hydrogen-bonded columns through charge-assisted N-H...O hydrogen bonds. Compound (II) packs in a chiral space group and forms helical one-dimensional hydrogen-bonded columns with 21 symmetry, consisting of repeating R43(10) hydrogen-bonded rings that are commonly observed in ammonium carboxyl­ate salts con­tain­ing chiral mol­ecules. This hydrogen-bond pattern, which has been observed repeatedly in ammonium carboxyl­ate salts, thus provides a means of producing chiral crystal structures from achiral mol­ecules.