A density functional theory and quantum theory of atoms in molecules study on hydrogen bonding interaction between paracetamol and water molecules

Abstract

To consider the hydrogen bonding interactions between paracetamol and water molecules, probable complexes of paracetamol from three active sites (carbonyl oxygen atom, hydroxyl oxygen atom, and nitrogen atom) with H₂O molecule were formed. The optimized geometries and total energies have been obtained at the B3PW91/6-31+G(d, p) level of theory. Comparison of hydrogen bond lengths and the energies of complexes showed hydrogen bond that form between the oxygen atom of the carbonyl group and hydrogen atom is stronger than others. Moreover, an increase in the number of hydrogen bonds increases stability of paracetamol-water complexes. At the end, the QTAIM was applied to explain the nature of the hydrogen bonds and confirm the more stability by complexation.