Effect of pressure up to 5.5GPa on dry powder samples of chlorpropamide form-A

The effect of pressure up to 5.5GPa on a dry powder sample of chlorpropamide (4-chloro-N-((propylamino)-carbonyl)-benzenesulfonamide), form-A (sp. gr. P2(1)2(1)2(1), a=9.066A, b=5.218A, c=26.604A), was studied in situ in a Merrill-Bassett diamond anvil cell using high-resolution X-ray powder diffraction (a synchrotron radiation source at SNBL ESRF, Grenoble). No evidence of the polymorphic transformation of chlorpropamide form-A to form-C was observed. The A-C polymorphic transition on tabletting previously reported by is therefore likely to be due to local heating effects. Similarly, the phase transitions of form-A reported by to be induced by pressure applied to a sample in its saturated ethanol solution (at 0.9 and at 2.0GPa) would appear to be solvent-mediated. In the dry sample, a phase transition may be supposed to occur at pressures above 4GPa, but this requires further studies.