Abstract
In this paper, the main features of Raman spectroscopy, one of the first
choice methods in the study of polymorphism in pharmaceuticals, are
presented taking chlorpropamide as a case of study. The antidiabetic
drug chlorpropamide (1-4-chlorobenzenesulphonyl-3-propyl urea),
which belongs to the sulfonylurea class, is known to exhibit, at least,
six polymorphic phases. These forms are characterized not only by
variations in their molecular packing but also in their molecular
conformation. In this study, the polymorphism of chlorpropamide is
discussed on the basis of Raman scattering measurements and quantum
mechanical calculations. The main spectroscopic features that
fingerprint the crystalline forms are correlated with the corresponding
crystalline structures. Using a theoretical approach on the energy
dependence of the conformers, simulated molecular torsion angles are
plotted versus the formation energy, which provides a satisfactory
agreement between the torsion angles at the energy minima and the
experimental values observed in the different solid forms of
chlorpropamide. Copyright (C) 2011 John Wiley & Sons, Ltd.
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