Do 1,2-ethanediol and 1,2-dihydroxybenzene present intramolecular hydrogen bond?

A study of the intramolecular hydrogen bond (IHB) in 1,2-ethanediol and 1,2-dihydroxybenzene ( catechol) was carried out using the QTAIM theory. Atomic and bond properties defined within this theory were calculated for different donor-acceptor distances, H-d ... O-a, in both molecules, and different H-O-a-C-C dihedral angles for 1,2-dihydroxybenzene, optimising the remaining geometry. Though no conformer of both compounds present IHB, it appears when the H-d ... O-a distance is reduced in both molecules or when the H-O-a-C-C angle is rotated in 1,2-dihydroxybenzene. The evolution of integrated and local properties follows the criteria of Koch and Popelier for hydrogen bond formation when the interatomic distance is modified, but display the opposite trends when the IHB is formed by rotating the dihedral angle.