title: Mefenamic acid anti-inflammatory drug: probing its polymorphs by vibrational (IR and Raman) and solid-state NMR spectroscopies.
abstract: This work deals with the spectroscopic (supported by quantum chemistry calculations), structural, and morphological characterization of mefenamic acid (2-[(2,3-(dimethylphenyl)amino] benzoic acid) polymorphs, known as forms I and II. Polymorph I was obtained by recrystallization in ethanol, while form II was reached by heating form I up to 175 °C, to promote the solid phase transition. Experimental and theoretical vibrational band assignments were performed considering the presence of centrosymmetric dimers. Besides band shifts in the 3345-3310 cm(-1) range, important vibrational modes to distinguish the polymorphs are related to out-of-phase and in-phase N-H bending at 1582 (Raman)/1577 (IR) cm(-1) and 1575 (Raman)/1568 (IR) cm(-1) for forms I and II, respectively. In IR spectra, bands assigned to N-H bending out of plane are observed at 626 and 575 cm(-1) for polymorphs I and II, respectively. Solid-state (13)C NMR spectra pointed out distinct chemical shifts for the dimethylphenyl group: 135.8 to 127.6 ppm (carbon bonded to N) and 139.4 to 143.3 ppm (carbon bonded to methyl group) for forms I and II, respectively.
authors.affiliation: Departamento de Química Fundamental, Instituto de Química, Universidade de São Paulo , Av. Prof. Lineu Prestes 748, CEP 05508-000, São Paulo-SP, Brazil.
authors.forename: Vanessa R R
authors.initials: VR
authors.lastname: Cunha
authors.forename: Celly M S
authors.initials: CM
authors.lastname: Izumi
authors.forename: Philippe A D
authors.initials: PA
authors.lastname: Petersen
authors.forename: Alviclér
authors.initials: A
authors.lastname: Magalhães
authors.forename: Marcia L A
authors.initials: ML
authors.lastname: Temperini
authors.forename: Helena M
authors.initials: HM
authors.lastname: Petrilli
authors.forename: Vera R L
authors.initials: VR
authors.lastname: Constantino
mesh_terms: D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000737:chemistry*; D003198:Computer Simulation; D003460:Crystallization; D000431:Ethanol / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008528:Mefenamic Acid / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D008956:Models, Chemical; D015394:Molecular Structure; D044367:Phase Transition; D017550:Spectroscopy, Fourier Transform Infrared; D013059:Spectrum Analysis, Raman; D013696:Temperature; D014732:Vibration; D014961:X-Ray Diffraction
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D008528:Mefenamic Acid; D000431:Ethanol