Comparison of Tautomerization, Vibrational Spectra and UV-Vis Analysis of β-Ketoester With Acetylacetone. An Experimental and Theoretical Study

Abstract

In this study, the equilibrium constants, keto-enol ratio, and hydrogen bond strength among keto and cis-enol forms of acetylacetone (AA), methyl acetoacetate (MAA), ethyl acetoacetate (EAA), ethyl 2-methyl acetoacetate (EMA), benzyl acetoacetate (BAA), and ethyl benzoyl acetone (EBA) have been investigated using density functional theory (DFT), compared with the experimental results. According to the obtained results, the relative energy of cis-enol and keto forms of β-ketoesters in gas phases is greater than that of acetylacetone, so the enol form of acetylacetone is more stable and it causes to increase its strength of intramolecular hydrogen bond. The electronic properties of these compounds were surveyed by NMR, FT-IR, and UV-Vis spectra. Besides, the obtained outcomes showed that the keto forms of β-ketoesters in the presence of acetonitrile and carbon tetrachloride as a solvent have a high absorption coefficient due to the polarity of the solvent.