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Issue 11, 2010
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Conformational and enantiotropic polymorphism of a 1 : 1 cocrystal involving ethenzamide and ethylmalonic acid

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Abstract

Polymorphism in cocrystals is increasingly gaining interest because of the overwhelming interest in pharmaceutical cocrystals. In this paper, we report a 1 : 1 cocrystal of an analgesic drug, ethenzamide (EA), with ethylmalonic acid (EMA) which exists in two polymorphic forms. Both the polymorphs were characterized by various analytical techniques, such as single-crystal and powder X-ray diffraction, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), hot-stage microscopy (HSM) and variable temperature X-ray diffraction (VTXRD). Crystal structure analysis suggests that the EMA molecules in both the polymorphs adopt different conformations but feature a common hydrogen bonding motif. Thermal analysis suggests that the polymorphs are related enantiotropically. Based on the information obtained from the thermal data and various other experiments, a semi-schematic energy-temperature diagram was constructed. Interestingly, it was observed that the polymorphic outcome of solid-state grinding is remarkably dependent on the polarity of the solvent used in the solvent-drop grinding experiments.

Graphical abstract: Conformational and enantiotropic polymorphism of a 1 : 1 cocrystal involving ethenzamide and ethylmalonic acid

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Article information


Submitted
22 Mar 2010
Accepted
11 May 2010
First published
07 Jul 2010

CrystEngComm, 2010,12, 3691-3697
Article type
Paper

Conformational and enantiotropic polymorphism of a 1 : 1 cocrystal involving ethenzamide and ethylmalonic acid

S. Aitipamula, P. S. Chow and R. B. H. Tan, CrystEngComm, 2010, 12, 3691
DOI: 10.1039/C004491A

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