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Polymorphism on leflunomide: stability and crystal structures.

Daniel Vega·Alicia Petragalli·Daniel Fernández·Javier A Ellena
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Abstract

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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Anti-Inflammatory Agents, Non-SteroidalCalorimetry, Differential ScanningCrystallizationDrug StabilityEthanolHydrogen BondingIsomerismIsoxazolesLeflunomideMicroscopy, PolarizationModels, MolecularSolutionsSolventsSpectrophotometry, UltravioletX-Ray DiffractionJournal ArticleResearch Support, Non-U.S. Gov't

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Daniel Vega, Alicia Petragalli, Daniel Fernández, Javier A Ellena. 2006. Polymorphism on leflunomide: stability and crystal structures.. https://doi.org/10.1002/jps.20382

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