Hydrogen-bonded complexes protocatechualdehyde - acetone in carbon tetrachloride: NMR-spectroscopy and molecular dynamics simulation

Abstract A comprehensive study of the hydrogen-bonded complexes of protocatechualdehyde – acetone formed in an inert solvent was carried out. Concentration dependences of the 1H NMR chemical shifts of protocatechualdehyde in carbon tetrachloride – acetone‑d6 mixtures were obtained. The most probable structures of hydrogen-bonded protocatechualdehyde-acetone complexes were determined by means of all-atomic molecular dynamics simulation. Using the GIAO/DFT (Gauge-Independent Atomic Orbital/Density Functional Theory) approach, the proton chemical shifts of the complexes were calculated within the framework of the (если она не единственная такая, то a) continuum model of the solvent, as well as with an explicit solvent. The parameters obtained from quantum-chemical calculations were used to interpret the experimentally observed dependences. It is shown that protocatechualdehyde forms predominantly hydrogen-bonded complexes with a composition of 1:1 in a binary solvent. The hydrogen atom of the hydroxyl group in the para-position takes part in the formation of the intermolecular hydrogen bond with acetone, while the hydrogen atom of the hydroxyl group in the meta-position is involved in the formation of an intramolecular hydrogen bond.