Theoretical and Experimental Investigation of the 2-Hydroxyquinoxaline Structure: Study of the Tautomerization Equilibrium System and Analysis of the Electronic Properties

All reasonable tautomers of 2-hydroxyquinoxaline (2HQ) are investigated by the DFT B3LYP/6-311G( d ) method. The optimized geometries corresponding to the minimum energy show that the keto form QX2 is the most stable form. The geometry optimization parameters (bond lengths, bond angles) are compared to the X-ray values. Calculated FTIR, UV, and NMR spectra of QX2 are compared to the experimental data to achieve a synergetic computational and spectroscopic approach for the structure analysis of 2HQ. The electronic properties, frontier molecular orbitals, and Mulliken atomic charges are calculated.