Polymorphism on leflunomide: stability and crystal structures.
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.
Unidad de Actividad Física, Comisión Nacional de Energía Atómica, Av. Gral. Paz 1499, 1650 San Martín, Buenos Aires, Argentina.
Daniel
D
Vega
Alicia
A
Petragalli
Daniel
D
Fernández
Javier A
JA
Ellena
D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000737:chemistry*; D002152:Calorimetry, Differential Scanning; D003460:Crystallization; D004355:Drug Stability; D000431:Ethanol; D006860:Hydrogen Bonding; D007536:Isomerism; D007555:Isoxazoles / Q000737:chemistry*; D000077339:Leflunomide; D008859:Microscopy, Polarization; D008958:Models, Molecular; D012996:Solutions; D012997:Solvents; D013056:Spectrophotometry, Ultraviolet; D014961:X-Ray Diffraction
D000894:Anti-Inflammatory Agents, Non-Steroidal; D007555:Isoxazoles; D012996:Solutions; D012997:Solvents; D000431:Ethanol; D000077339:Leflunomide