Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
2487953 | Journal of Pharmaceutical Sciences | 2006 | 14 Pages |
Abstract
The crystal structure of carnidazole form II, Oâmethyl [2â(2âmethylâ5ânitroâ1Hâimidazoleâ1âyl)ethyl]thiocarbamate, has been determined using synchrotron Xâray powder diffraction in combination with simulated annealing and whole profile pattern matching, and refined by the Rietveld method. For structure solution, 12 degrees of freedom were defined: one motion group and six torsions. Form II crystallizes in space group P21/n, Zâ=â4, with unit cell parameters after Rietveld refinement: aâ=â13.915(4), bâ=â8.095(2), câ=â10.649(3) Ã
, βâ=â110.83(1)°, and Vâ=â1121.1(5) Ã
3. The two polymorphic forms, as well as the hydrate, crystallize in the monoclinic space group P21/n having four molecules in the cell. In form II, the molecules are held together by forming two infinite zigâzag chains via hydrogen bonds of the type NâHââ¦âN, the same pattern as in form I. A conformational study of carnidazole, at semiempirical PM3 level, was performed using stochastic approaches based on modification of the flexible torsion angles. The values of the torsion angles for the molecules of the two polymorphic forms and the hydrate of carnidazole are compared to those obtained from the conformational search. Form I and form II are enantiotropic polymorphic pairs this agrees with the fact that the two forms are conformational polymorphs.
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Authors
Héctor Novoa de Armas, Oswald M. Peeters, Norbert Blaton, G.u.y. Van den Mooter, Dirk J.A. De Ridder, Henk Schenk,