title: Polymorphic differences in alpha- and beta-form crystals of 2R, 4S, 6-fluoro-2-methyl-spiro[chroman-4,4'-imidazoline]-2',5-dione (M79175) as determined by X-ray diffraction, infrared spectroscopy, and differential scanning calorimetry.
abstract: Polymorphic differences in alpha- and beta-form crystals of 2R, 4S, 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 alpha- and beta-form crystals, respectively. The infrared spectra showed the absorption band assigned to NH streching vibration for the alpha-form crystals to be centered at 3250 cm-1 and that for the beta-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 beta- to alpha-form was observed at various heating rates, which were enhanced by the presence of a small amount of alpha-form crystals previously added to the beta-form. The former appeared to serve as a source of nuclei for the growth of both forms. These results confirm that the alpha-form crystal is more stable than the beta-form.
authors.affiliation: Department of Physical Chemistry, Eisai Company, Ltd., Ibaragi, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Ashizawa
authors.forename: K
authors.initials: K
authors.lastname: Uchikawa
authors.forename: T
authors.initials: T
authors.lastname: Hattori
authors.forename: T
authors.initials: T
authors.lastname: Sato
authors.forename: Y
authors.initials: Y
authors.lastname: Miyake
mesh_terms: D002152:Calorimetry, Differential Scanning; D003460:Crystallization; D007093:Imidazoles / Q000032:analysis*; D048289:Imidazolidines; D008968:Molecular Conformation; D011108:Polymers; D013055:Spectrophotometry, Infrared; D014961:X-Ray Diffraction
chemical_list: D007093:Imidazoles; D048289:Imidazolidines; D011108:Polymers; C037070:M 79175