Experimental and Theoretical Studies on Tautomerism and Acid-Base Behavior of N-(2-Oxo-2H-chromen-3-yl)acetamide

The structures of all of the chemical species involved in the prototropic tautomerism and acid base dissociation equilibria of N-(2-oxo-2H-chromen-3-yl)acetamide were determined both experimentally and theoretically. Using the calculated acidity constants, the prototropic equilibrium constants for keto-enol tautomerizm were determined. The enolate and the keto-amino forms were found to be predominant. The gauge including atomic orbital method for calculating H-1 and C-13 NMR nuclear magnetic shielding tensors at both the Hartree-Fock and density functional levels of theory was applied to N-(2-oxo-2H-chromen-3-yl)acetamide. The obtained theoretical data were compared to the experimental data. A satisfactory agreement between the experimental chemical shifts and the theoretical values of shielding constants were obtained. Acceptable correlations were presented between experimental and theoretical results.