4-Aminocoumarin 2 was prepared in high yield via solventless reaction. The structure of the 2
was determined with single crystal X-ray analysis. The detailed NMR and IR spectra were
reported for the first time. DFT calculations [B3LYP/6-31+G**] showed good agreement
between the theoretical and experimental values for the optimized and X-ray structures, as well
as between the vibrational and NMR spectroscopy. The thermodynamic pKBH+ values were
calculated using three different methods: Yates and McClelland (with HA acidity functions),
Excess Acidity Method and Bunnett and Olsen Method. The experimental and theoretical data
presented are consistent with the weak nucleophilic properties of 2.