Caracterização do ácido isoftálico (C8H6O4) por meio de espectroscopia Raman

Abstract

Isophthalic acid (C8H6O4) is an aromatic dicarboxylic compound of great industrial importance, especially in the production of polymers, resins, and plasticizers. This work aimed to characterize isophthalic acid crystals obtained by the slow solvent evaporation method. The crystalline structure was confirmed by single-crystal X-ray diffraction as monoclinic (space group P21/c). Thermal analysis (TG/DSC) revealed high stability up to approximately 300◦C, with a melting and decomposition event near 350◦C. Raman spectroscopy under ambient conditions, combined with density functional theory (DFT) calculations, allowed the identification of vibrational modes associated with the aromatic ring, carboxylic groups, and lattice vibrations. An excellent agreement was observed between experimental and theoretical spectra, confirming the reliability of the computational approach. Key modes were identified in the regions of 0–300 cm⁻¹ (lattice modes), 300–900 cm⁻¹ (ring deformations and breathing), 1200–1800 cm⁻¹ (C=O, C–O, and C–C stretches coupled to OH deformations), and 3000–3200 cm⁻¹ (C–H stretches). The results provide a comprehensive vibrational and thermal characterization of isophthalic acid, supporting its use in advanced material applications.