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Polymorphism on leflunomide: Stability and crystal structures

✍ Scribed by Daniel Vega; Alicia Petragalli; Daniel Fernández; Javier A. Ellena

Publisher
John Wiley and Sons
Year
2006
Tongue
English
Weight
274 KB
Volume
95
Category
Article
ISSN
0022-3549

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✦ Synopsis

Two polymorphs of Leflunomide were found and studied (form I and II). Both of them were characterized by X-ray powder diffraction and thermal analysis. Single crystals were obtained and both structures were solved. Forms I and II crystallize in the space group P2(1)/c with two and one independent molecules per asymmetric unit, respectively. Thermodynamic stability of the two forms is assessed by differential scanning calorimetry. The cohesion in the crystal of form I (the more stable) is provided by both by H bonding as well as pi...pi interactions, while in form II it is given only by the former. The independent molecules in form I adopt different conformations thus allowing for a larger number of intermolecular interactions.

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