Conformational stability, equilibrium constant between two stable cis-enol forms, and intramolecular hydrogen bonding (IHB) of benzoylacetone (BA) and p-substituted benzoylacetone (X-BA), where X=NO2, OCH3, CH3, OH, CF3, Cl, F, and NH2, have been investigated by means of density functional theory (DFT) calculations and compared with the reported experimental results. According to our calculations, the energy difference between the two stable chelated enol forms is negligible, about 0.35-1.1 kcal/mol ranges in the gas phase and different solvents. The electronic effects of p-substituted benzoylacetone on IHB strength were determined and established by NMR, IR spectra, geometry, and topological parameters with Hammett linear free energy relationships. Also, the linear correlation coefficients between σp and selected parameters related to IHB strength, such as geometrical, topological parameters, IR and NMR spectroscopic data, and NBO results related to IHBs were considered. Good linear correlations between σp and the mentioned parameters were obtained

Keywords