INVESTIGATION OF BASICITY AND PROTONATED SITES OF SOME COUMARIN DERIVATIVES A DFT STUDY

Abstract

Hymecromone and umbelliferone are hydroxycoumarin compounds, which are highly significant because of their wide applications in organic chemistry, medicine, and industry. They show photochemical, antagonist, anticoagulants, anticancer, antioxidant, antiviral, and antimicrobial properties. The ground-state equilibrium geometries of two molecules and their protonated forms were optimized at the density functional theory (DFT)/6-311++G(d) level of theory. Proton affinities on two protonated sites of the studied compounds were calculated at the DFT/ B3LYP / 6-311++G(d). The results indicated that heterogeneous oxygen atom in lactonic ring was strongly favored over hydroxy oxygen atom as sites of protonation for the series studied. A comprehensive investigation of the effect of solvent on the process of protonation of the studied compounds was performed using CPCM method at the B3LYP/6-311++G(d) level of theory. The results showed that the solvent increased the dipole moments of the bare molecules compared with the gas phase and the solvation was enhanced in a protic polar solvent such as water and ethanol.