Study of the dehydroacetic acid homolog by IR, Raman spectroscopy, and DFT

Abstract

The IR and Raman spectra of 3-(3,3-Dimethylbutanoyl)-4-hydroxy-6-neopentyl-2H-pyran-2-one (1) in the crystalline state have been studied. The tautomerization of 1 was carried out by a quantum-chemical method at the DFT/B3LYP/6-311G** level. The experimental IR and Raman spectra of compound 1 are reproduced by calculations for the 4-hydroxy enol tautomer (A). The classification of the bands in the experimental vibrational spectra of 1 has been carried out. The intramolecular H-bond was characterized by IR spectroscopy. The free energies of the tautomers and their populations were calculated for two different solvents. HOMO and LUMO of molecule 1 are located on the pyran ring. During tautomeric transformations, there is a significant delocalization of charge and a change in the reactivity of the molecule. The reactivity of the pyrone 1 was characterized using descriptors. The enol form B was found to have higher ionization energy, electron affinity, chemical potential, and electrophilic index than the enol A form. The dipole moment is higher for form A, and the softness of the two molecules is the same.