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E. Horn, and M. Kurahashi
[Advances in X-Ray Chem. Analysis, Vol.25, pp.83-94, 1994]
The crystal and molecular structure of 8-aminocaprylic acid was determined from X-ray powder diffraction. The flowchart is shown in Fig.1. Before analysis the powder sample was recrystallized and pulverized to maximize the crystallinity and minimize preferred orientation effects, respectively. In addition, the sample was pressure packed into a disc to increase the packing density and therefore also the signal-to-noise ratio. The diffraction data was collected on a transmission type Guinier diffractometer which was recently developed. The compound crystallizes in the monoclinic space group P21/n with a=4.614(1), b=7.516(1), c=24.953(1) Å and beta=90.67(1)°. A partial solution was obtained from the direct methods programs SHELXS-86 and MULTAN-78. The complete molecule was obtained by adding the remaining non-hydrogen atoms by molecular modelling. The final Rietveld refinement, with the hydrogen atoms fixed at calculated positions, converged at the respective reliability indices Rwp=13.8% and Rf=4.2%. The crystal lattice consists of 8-aminocaprylic acid molecules aligned parallel to the c-axis. An extensive 3-dimensional O...H-N type hydrogen bonding network exists between neighboring molecules.
