Journal
ACTA CRYSTALLOGRAPHICA SECTION B-STRUCTURAL SCIENCE
Volume 66, Issue -, Pages 76-80Publisher
WILEY-BLACKWELL
DOI: 10.1107/S0108768109047363
Keywords
ibuprofen; X-ray powder diffraction; rigid-body constraints
Categories
Funding
- Hubert Curien partnership PESSOA
- Region Nord/Pas de Calais
- INTER-RREG (FEDER)
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Annealing of the quenched ibuprofen at 258 K yielded a new crystalline form, called phase II. Powder X-ray diffraction patterns of this phase II were recorded with a laboratory diffractometer equipped with an INEL G3000 goniometer and a curved position-sensitive detector CPS120. The starting structural model was found by a Monte-Carlo simulated annealing method. The final structure was obtained through Rietveld refinements with rigid-body constraints for the phenyl group and soft restraints on the other interatomic bond lengths and bond angles. The cell volume is 5% larger than that of the conventional phase I at 258 K. It is also shown that the orientation of the propanoic acid group is drastically changed with respect to phase I, leading to strong modifications of the orientation of the O-H center dot center dot center dot O hydrogen bonds with respect to the chains of dimers. These structural considerations could explain the metastable character of this phase II.
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