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

The effect of pressure up to 5.5 GPa on a dry powder sample of chlorpropamide (4-chloro-N-((propylamino)-carbonyl)-benzenesulfonamide), form-A (sp. gr. P212121, a = 9.066 Å, b = 5.218 Å, c = 26.604 Å), 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 Otsuka et al. (1989) is therefore likely to be due to local heating effects. Similarly, the phase transitions of form-A reported by Cao (2002) to be induced by pressure applied to a sample in its saturated ethanol solution (at 0.9 and at 2.0 GPa) would appear to be solvent-mediated. In the dry sample, a phase transition may be supposed to occur at pressures above 4 GPa, but this requires further studies.