Experimental and theoretical investigation of 2-hydroxy-5-methoxybenzoic acid by vibrational spectroscopy

FT-IR and Raman spectra of 2-Hydroxy-5-Methoxybenzoic Acid (2H5MBA) have been experimentally reported in the region of 4000-10 cm-1 and 4000-50 cm-1 , respectively. The optimized geometric parameters (bond distances, bond and dihedral angles), normal mode frequencies and corresponding vibrational assignments and vibrational spectrums, potential energy distributions (PED) belonging to vibrational assignments, conformational equilibria, some thermodynamics functions, the highest occupied and the lowest unoccupied molecular orbitals (HOMO and LUMO) of 2H5MBA (C8H8O4) are theoretically examined by means of B3LYP hybrid density functional theory (DFT) method together with 6-31G(d) and 6-31++G(d,p) basis sets. Calculations are assumed for six different conformations of 2H5MBA, both in gas and in solution phase. In order to investigate the solvent effect chloroforom and as non-polar solvent and dimethylsulfoxide as polar solvent were used.It has been seen that obtained experimental and theoretical results for 2H5MBA are in good agreement with each other. The quantum chemical calculations applied are well and sufficient levels for vibrational frequencies and corresponding vibrational assignments. IR and Raman intensities of the title molecule depend on the solvent and medium whereas its conformation is solvent and medium independent.