Abstract Molecular structure, conformational stabilities, and intramolecular hydrogen bonding (IHB) of 4,4-dimethyl-1-phenylpentane-1,3-dione (DMPD), have been investigated by means of density functional theory (DFT) calculations and experimental results. The geometries and electronic energies of different cis-enol forms of DMPD have been obtained with the ab initio (MP2 level) and DFT (B3LYP and TPSSh levels) methods, using various basis sets. The energy differences between three stable E1, E2, and E3 chelated enol forms are negligible. According to the theoretical calculations, DMPD has a hydrogen bond strength of about 16.8 kcal/mol, calculated at the B3LYP/6-311++G** level, which is about 0.7 kcal/mol stronger than that of benzoylacetone (BA). The theoretical and experimental results obtained for stable enol forms of DMPD have been compared with each other and also with those of BA and 5,5-dimethylhexane-2,4-dione (DMHD). The molecular stability and the hydrogen bond strength were investigated by applying the NBO, topological analysis, geometry calculations, and spectroscopic results.

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