Thermodynamic relationship between alpha- and beta-forms of crystalline progesterone.

Thermodynamic properties such as the latent heat of fusion, aqueous solubility, heat of solution, and interchange energy with water were determined for single crystals of progesterone in alpha- and beta-forms. The differences in the properties between the polymorphic crystals arise from a dissimilar mode of molecular packing, rather than of molecular conformation, in the unit cells, as reflected in the IR spectral and X-ray crystallographic results..