Acta Crystallographica Section B

Volume 65, Part 6 (December 2009)

research papers

Acta Cryst. (2009). B65, 770-781 [ doi:10.1107/S010876810903290X ]

A conformational polymorphic transition in the high-temperature -form of chlorpropamide on cooling: a new '-form

T. N. Drebushchak, Y. A. Chesalov and E. V. Boldyreva

Abstract: Structural changes in the high-temperature [epsilon] -polymorph of chlorpropamide, 4-chloro-N-(propylaminocarbonyl)benzenesulfonamide, C₁₀H₁₃ClN₂O₃S, on cooling down to 100 K and on reverse heating were followed by single-crystal X-ray diffraction. At temperatures below 200 K the phase transition into a new polymorph (termed the [epsilon] '-form) has been observed for the first time. The polymorphic transition preserves the space group Pna2₁, is reversible and is accompanied by discontinuous changes in the cell volume and parameters, resulting from changes in molecular conformation. As shown by IR spectroscopy and X-ray powder diffraction, the phase transition in a powder sample is inhomogeneous throughout the bulk, and the two phases co-exist in a wide temperature range. The cell parameters and the molecular conformation in the new polymorph are close to those in the previously known [alpha] -polymorph, but the packing of the z-shaped molecular ribbons linked by hydrogen bonds inherits that of the [epsilon] -form and is different from the packing in the [alpha] -polymorph. A structural study of the [alpha] -polymorph in the same temperature range has revealed no phase transitions.

Keywords: polymorphism; chlorpropamide; molecular conformation; hydrogen bonds.


	Structure factor file (CIF format) (96.2 kbytes) [ doi:10.1107/S010876810903290X/gp5033enewcpa100sup2.hkl ] Contains datablock enewcpa100

	Structure factor file (CIF format) (72.1 kbytes) [ doi:10.1107/S010876810903290X/gp5033ecpa250sup3.hkl ] Contains datablock ecpa250

	Structure factor file (CIF format) (57.2 kbytes) [ doi:10.1107/S010876810903290X/gp5033enewcpa200sup4.hkl ] Contains datablock enewcpa200

	Structure factor file (CIF format) (115.4 kbytes) [ doi:10.1107/S010876810903290X/gp5033acpa105sup5.hkl ] Contains datablock acpa105

	Structure factor file (CIF format) (105.1 kbytes) [ doi:10.1107/S010876810903290X/gp5033acpa200sup6.hkl ] Contains datablock acpa200

	Structure factor file (CIF format) (119.6 kbytes) [ doi:10.1107/S010876810903290X/gp5033acpa295sup7.hkl ] Contains datablock acpa295

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