Crystallization and disorder of the polytypic α<subscript>1</subscript> and α<subscript>2</subscript> polymorphs of piroxicam.
In: CrystEngComm, Jg. 17 (2015-07-28), Heft 28, S. 5266-5272
Online
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Zugriff:
Polymorphism of the active pharmaceutical ingredient piroxicam, C 15 H 13 N 3 O 4 S, is investigated with an aim to clarify the identity and crystallization conditions of the α 1 and α 2 polymorphs. The structures are polytypic, containing identical 2-dimensional layers, with different symmetry relationships between the layers. The α 1 structure is orthorhombic and non-centrosymmetric (space group type Pca2 1 ), while the α 2 structure is monoclinic and centrosymmetric (space group type P2 1 /c). α 2 can be crystallized by evaporation from ethanol at 25 °C, while α 1 is obtained by crystallization from the same solvent at 4 °C. The polytypic relationship provides a suitable condition for order–disorder phenomena to be observed in single crystals. Intermolecular interaction energies calculated using the PIXEL method suggest that the centrosymmetric interlayer regions in α 2 involving the pyridyl groups are more stabilising than the corresponding non-centrosymmetric interlayer regions in α 1 . This is consistent with observations of inversion twinning in non-centrosymmetric α 1 crystals. The interlayer regions involving the benzothiazine groups have very similar interaction energies in the two structures. [ABSTRACT FROM AUTHOR]
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Titel: |
Crystallization and disorder of the polytypic α<subscript>1</subscript> and α<subscript>2</subscript> polymorphs of piroxicam.
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Autor/in / Beteiligte Person: | Upadhyay, Pratik P. ; Bond, Andrew D. |
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Zeitschrift: | CrystEngComm, Jg. 17 (2015-07-28), Heft 28, S. 5266-5272 |
Veröffentlichung: | 2015 |
Medientyp: | academicJournal |
ISSN: | 1466-8033 (print) |
DOI: | 10.1039/c5ce00050e |
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