Abstract:
Using in situ polarization microscopy
and in situ Raman spectroscopy, a polymorphic phase transition from the
triclinic to the monoclinic crystal form of
7-alpha-methyl-Delta5,10-norethindrone
has been observed in acetone solutions at room temperature. The metastable
triclinic form is nucleated epitaxially on the stable monoclinic form beyond
a threshold supersaturation. The metastable phase transforms into the stable
phase by a solid-solute-solid mechanism in acetone. The thermodynamics
of ordinary and epitaxial nucleation are discussed.