FURTHER CHARACTERIZATION OF THE SOLID FORMS OF IOPANOIC ACID AND ITS ENANTIOMERS

The enantiomers of iopanoic acid were purified by crystallization and characterized by optical rotation, DSC, IR spectra, X-ray powder diffraction, and chiral HPLC. (-R)-enantiomer: {[alpha]20D = -6.1-degrees, mp. = 165.4-degrees-C; (+S)-enantiomer: [alpha]20D = + 6.2-degrees, mp. = 165.6-degrees-C. The IR spectra and X-ray patterns are fingerprints. Chiral HPLC (isocratic method, mobile phase: ethanol/nhexane, 2/98 with 0.5\% acetic acid) gave a resolution = 0.98 and a 99.6\% recovery. From X-ray and thermal analyses the racemate Form I, mp. = 153.8-degrees-C, resulted to be a racemic compound. The binary phase diagram between the enantiomers and the racemic compound was constructed from the phase transition temp. obtained by DSC heating curves of appropriate mixtures. At a given enantiomer ratio (71/29) a eutectic compound, mp. = 144.7-degrees-C, is formed. In the range 88-100\% a solid solution between the components is observed.}