PHASE-TRANSITIONS INVOLVING REORDERING OF THE GUEST MOLECULES IN A SOLID ORGANIC INCLUSION COMPOUND - HEPTANOIC ANHYDRIDE-UREA

Phase transitions below ambient temperature in the heptanoic anhydride -urea inclusion compound have been investigated using X-ray diffractio n and differential scanning calorimetry; one of these phase transition s (at ca. 179 K on cooling)is associated with a change in the mode-of three-dimensional ordering of the heptanoic anhydride guest molecules with no detectable change in the host (urea):structure, and represents the first reported example of this type of phase transition for urea inclusion compounds.