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Inicio » Actividades I+D > Publicaciones 2006 > Polymorphism on Leflunomide: Stability a...
artículo con referato
"Polymorphism on Leflunomide: Stability and Crystal Structures"
D. Vega, A. Petragalli, D. Fernández and J. Ellena
J. Pharm. Sci. 95(5) (2006) 1075-1083
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 P21/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 ππ 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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