K. Ashizawa, K. Uchikawa, T. Hattori
Jul 1, 1988
Citations
0
Influential Citations
7
Citations
Journal
Journal of Pharmaceutical Sciences
Abstract
Abstract Polymorphic differences in α - and β-form crystals of 2 R , 4 S , 6-fluoro-2-methyl-spiro[chroman-4,4′-imidazoline]-2′,5-dione (M79175; 1) were studied by X-ray diffractometry, infrared spectroscopy, and differential scanning calorimetry. X-ray powder diffraction indicated the longest spacing of the unit cells to be 14.9 and 12.4 A for the α - and β-form crystals, respectively. The infrared spectra showed the absorption band assigned to NH streching vibration for the α -form crystals to be centered at 3250 cm −1 and that for the β-form crystals to split into two peaks, at 3150 and 3425 cm −1 . The enthalpies of fusion were 26.3 kJ/mol at 517.5 K and 31.3 kJ/mol at 501.0 K, respectively. Transformation from the β- to α -form was observed at various heating rates, which were enhanced by the presence of a small amount of α -form crystals previously added to the β-form. The former appeared to serve as a source of nuclei for the growth of both forms. These results confirm that the α -form crystal is more stable than the β-form.