Crystal pseudopolymorphism of secnidazole bulk drug, C7H11N3O3

An indexed powder diffraction pattern and related crystallographic data are reported for secnidazole [C7H11N3O3, IUPAC name: 1-(2-hydroxypropyl)-2-met hyl-5-nitroimidazole], which is not represented in the Powder Diffraction F ile. The unit cell dimensions were determined from diffractometer methods, using monochromatic CuK alpha(1) radiation, and evaluated by indexing progr ams. The monoclinic cell found for 1-(2-hydroxypropyl)-2-methyl-5-nitroimid azole is: a = 12.426(2) Angstrom, b = 12.173(2) Angstrom, c = 6.656(1) Angs trom, beta = 100,19(1)degrees, Z = 4, space group P2(1)/c (No. 14), D-x = 1 .271 g/cm(3). Crystallization of an anhydrous powdered sample of secnidazol e in a buffer solution of Na2B4O7 and NaOH (pH 10.4) resulted in crystals t hat contained water of crystallization as shown by single crystal structure determination. Secnidazole exhibits crystal pseudopolymorphism, because th e experimental powder pattern of the anhydrous form. and the calculated pat tern from the structure determination of the hydrate form are similar. Obse rved powder diffraction data for this drug were interpreted with the aid of a calculated pattern based upon the crystal structure determined. The cell found by TREOR90P for anhydrous secnidazole is in good agreement with that of the hemihydrate form determined from single crystal diffraction: a = 12 .424(2) Angstrom, b = 12.187(2) Angstrom, c = 6.662(1) Angstrom, beta = 100 .9(1)degrees; Z = 4. (C) 1999 International Centre for Diffraction Data. [S 0885-7156(98)01003-3].