In this paper, the structure and vibrational spectra of dihydroxybenzoic acid isomers and their dimers are modeled using the density functional theory B3LYP/6-31G(d) using the GAUSSIAN software package: the minimum energy, the geometric structure, the components of the dipole moment, the frequencies of normal vibrations, their intensities in the IR spectrum are calculated. The simulation results indicate a strong influence on the IR spectra of the isomers of intermolecular hydrogen bonds, manifested in an anomalous broadening of the bands and an increase in the intensity in the measured IR spectra in the region above 3000 cm-1. The hydrogen bond is assigned to the average type. It is established that intramolecular hydrogen bonds are manifested in the same region of the IR spectra of some isomers of DHBA. Based on the results obtained during the simulation, various isomers of DHBA were identified and their IR spectra were interpreted.
dihydroxybenzoic acid, DHBA, modeling, density functional theory method, IR spectrum, vibrational spectrum, frequency, intensity
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