Mefenamic Acid Anti-Inflammatory Drug: Probing Its Polymorphs by Vibrational (IR and Raman) and Solid-State NMR Spectroscopies

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• 作者：Vanessa R. R. Cunha ; Celly M. S. Izumi ; Philippe A. D. Petersen ; Alvicl茅r Magalh茫es ; Marcia L. A. Temperini ; Helena M. Petrilli ; Vera R. L. Constantino
• 刊名：Journal of Physical Chemistry B
• 出版年：2014
• 出版时间：April 24, 2014
• 年：2014
• 卷：118
• 期：16
• 页码：4333-4344
• 全文大小：645K
• 年卷期：v.118,no.16(April 24, 2014)
• ISSN：1520-5207

文摘

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 掳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鈥?310 cm^鈥? range, important vibrational modes to distinguish the polymorphs are related to out-of-phase and in-phase N鈥揌 bending at 1582 (Raman)/1577 (IR) cm^鈥? and 1575 (Raman)/1568 (IR) cm^鈥? for forms I and II, respectively. In IR spectra, bands assigned to N鈥揌 bending out of plane are observed at 626 and 575 cm^鈥? for polymorphs I and II, respectively. Solid-state ¹³C 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.