EFFECT OF GUEST SPECIES ON INCLUSION COMPOUND FORMATION OF DEOXYCHOLIC-ACID BY CO-GRINDING

Deoxycholic acid (DCA) was ground with a guest compound by using a vib rational mill. Powder X-ray diffraction, differential scanning calorim etry, and fluorescence spectroscopic data indicated the formation of t he inclusion complex in the ground mixture of DCA-phenanthrene and DCA -naphthalene systems. The DCA-naphthalene ground mixture was found to have higher crystallinity than the DCA-phenanthrene ground mixture, an d this was assumed to relate to the difference in the crystallization temperature of the inclusion complex. When low-temperature grinding wa s performed for DCA and other aromatic hydrocarbons dong with naphthal ene and phenanthrene, all the ground mixtures were obtained in amorpho us state. Crystallization of inclusion compounds from the amorphous gr ound mixtures was observed to occur at a higher temperature as the sto ichiometric ratio (DCA/guest) of the compound increased. With regard t o the formation of crystalline complex between DCA and a guest, such a s naphthalene, by grinding at room temperature, a two-step mechanism w as proposed: i.e., (i) amorphization of both DCA and guest crystals, a nd (ii) crystallization of the inclusion complex induced above a certa in temperature.