Effect of hydrogen bonding on the structure and vibrational spectra of hydroxybenzoic acids

Abstract

In this work, the B3LYP/6-31G(d) density functional theory method is used to model the structure and vibrational spectra of dimers of molecules of dihydroxybenzoic and hydroxybenzoic acids: the minimum energy, geometric structure, components of the dipole moment, frequencies of normal vibrations, and their intensity in the IR spectrum are calculated. Modeling was carried out using the GAUSSIAN software package: H-complexes of DHBA molecules consisting of two acid monomers were constructed in the Gaussview program, and their primary characteristics were obtained in the Gaussian program. The simulation results clearly show a strong influence on the IR spectrum of the intermolecular hydrogen bonds formed in the dimer ring, which manifests itself in anomalous broadening of the bands and an increase in intensity in the IR spectrum in the region of 3000 cm-1. The geometrical parameters of the dimers of HBA and DHBA correspond to those generally accepted. The hydrogen bond is of the middle type. From the results obtained during the simulation, it can be concluded that various isomers of HBA and DHBA can be identified based on the analysis of their IR spectra and, depending on this, the possible properties of a particular molecule, as well as its further application in various fields, can be assumed.

Speaker

Denis S. Finashkin
Saratov State University
Russia

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