Monoclinic and orthorhombic polymorphs of paracetamol—solid state linear dichroic infrared spectral analysis

Solid-state linear dichroic infrared (IR-LD) spectral analysis of both monoclinic (form I) and orthorhombic (form II) polymorphs of paracetamol was carried out using an orientation technique as a nematic liquid crystal suspension. The so-called reducing-difference procedure for polarized spectra interpretation was applied and the obtained supramolecular stereo structural data of both modifications were compared with known crystallographic ones. A detailed vibration assignment of characteristic frequencies of forms I and II was also applied. A quantitative FT-IR spectral approach for monoclinic form determination in mixtures by the intensity ratio of 1610 cmK1 peak (characteristic for both forms) to 1666 cmK1 one (attributed to orthorhombic modification) was presented, as well. q 2005 Elsevier B.V. All rights reserved