Preparation and crystal structure of a trihydrate of paracetamol.

This work reports the preparation and crystal structure of a trihydrate of paracetamol. Crystals were grown by slow cooling of an aqueous solution of paracetamol to 0 degrees C. Single-crystal X-ray diffraction shows that the trihydrate crystallizes in the orthorhombic crystal system, space group Pbca, Z = 8, a = 7.3324(16), b = 12.590(3), c = 22.636(6) A, V = 2089.7(9) A(3). The crystals of the trihydrate dehydrate rapidly at 20 degrees C to give anhydrous paracetamol as its monoclinic form. Copyright 2002 Wiley-Liss, Inc. and the American Pharmaceutical Association