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1 Polish Journal of Chemistry

1 2002

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The Role of Hydrogen Bonds in the Pressure-Induced structural Distortion of 4-Hydroxyacetanilide Crystals

Boldyreva E., Shakhtshneider T. P., Ahsbabs H., Uchtmann H., Burgina E. B., Baltakhinov V. P.

Polish Journal of Chemistry

2002

Vol. 76 / nr 9

1333-1346

Results of X-ray diffraction and IR-specroscopy studies of the role of hydrogen bonds in the structural distortion of the monoclinic and the orthorhombic polymorphs of paracetamol induced by hydrostatic pressure (up to 4-5 GPa) are analyzed. Two groups of phenomena were studied: (i) the anisotropic structural distortion of the same polymorph, (ii) transitions between the polymorphs induced by pressure. The bulk compressibilities of the two polymorphs are practically equal. The anisotropy of pressure-induced structural distortion is qualitatively different. Lattice expansion in particular crystallographic directions was observed for the monoclinic polymorph. With increasing pressure the intermolecular NH...O and OH...O hydrogen bonds contracted and the intramolecular angles between the planes of the phenyl ring and the acetamide group decreased. Pressure- induced transitions between the polymorphs were poorly reproducible and limited by nucleation of the new polymorph.