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A novel Raman spectroscopic approach to identify polymorphism in leflunomide: a combined experimental and theoretical study
Author(s) -
Sharma Poornima,
Gangopadhyay Debraj,
Umrao Sima,
Kumar Shiv,
Ghosh A. K.,
Mishra P. C.,
Singh Ranjan K.
Publication year - 2016
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.4834
Subject(s) - raman spectroscopy , differential scanning calorimetry , polymorphism (computer science) , leflunomide , chemistry , powder diffraction , scanning electron microscope , solubility , crystallography , diffraction , stereochemistry , analytical chemistry (journal) , materials science , thermodynamics , organic chemistry , biochemistry , physics , methotrexate , biology , genotype , optics , immunology , composite material , gene
Polymorphism is an important characteristic which affects the activity, solubility and other physical properties of a compound and can be induced by varying temperature, pressure and solvent. The presence and conversion of α to β polymorphic forms of an anti‐rheumatic drug leflunomide have been studied by temperature‐dependent and in situ Raman observations. Both α and β polymorphs were found to co‐exist in the temperature interval 367–372 K. The α form alone exists below 367 K and the β form alone above 373 K. The CO stretching band clearly demonstrates the α → β conversion because of breaking of N–H···O bond and formation of N–H···N bond. On cooling the Raman spectra suggest the irreversibility of this conversion. Thermodynamic stability, crystal parameters and surface morphology of both forms in the leflunomide powder used for the present study have been verified by differential scanning calorimetry, X‐ray powder diffraction and scanning electron microscopy. Copyright © 2015 John Wiley & Sons, Ltd.