Racemic species of sodium ibuprofen: Characterization and polymorphic relationships

Racemic and homochiral sodium ibuprofen were characterized by thermal analysis and powder X-ray diffractometry. The melting point phase diagram was constructed and thermodynamic calculation was performed. In contrast to racemic ibuprofen, which is a racemic compound, racemic sodium ibuprofen forms both a racemic conglomerate (termed the γ-form) as well as two polymorphic racemic compounds, α and β, which are less stable monotropes. From the supercooled liquid, α and β crystallized along with the original γ-form. Forms α and β are "enantiotropically related" with a transition temperature between 75° and 113°C, but can be considered to be metastable monotropes of the racemic conglomerate, the stable γ-form.