Influence of the structure and gas-phase acidity of aromatic disulfonic acids on proton transfer and the formation of hydrogen-bonded complexes with pyridine derivatives

Abstract

Listen

Translate article

The structure and conformational properties of a number of aromatic disulfonic acids were studied,using quantum chemistry methods (DFT(B3LYP)/cc-pVTZ). Their gas-phase acidity was assessed, and their hydrogen-bonded complexes with 4-pyridyl-4′-propyloxybenzoate were modeled in the variant with proton transfer from the sulfo group to pyridyl and without proton transfer. It has been shown that the gas-phase acidity of disulfonic acids is more pronounced than in the corresponding sulfonic acids due to competition between electron-withdrawing electron substituents. Modeling of the complexes was carried out in the gas phase and in solvents of different polarities. The potential proton transfer functions have two minima, corresponding to structures with and without proton transfer. The magnitude of the barrier and the relative energies of the complexes depend on the gas-phase acidity of benzene disulfonic acids: components with lower gas-phase acidity give a larger transition barrier and a larger difference in the energies of complexes with and without proton transfer. However, proton transfer complexes for such acids are characterized by the strongest hydrogen bonds.