Density Functional Theory Study of Intramolecular Hydrogen Bonding and Proton Transfer ino-Hydroxyaryl Ketimines

The potential energy surface and the reaction pathway for the intramolecular hydrogen transfer in o-hydroxyaryl ketimines are characterized using DFT methods. Structural changes in the proton-transfer process in quasi-aromatic hydrogen bonding are described. A transition state and a state with a low proton-transfer barrier were studied in sterically compressed o-hydroxyaryl ketimines (2(N-methyl-alpha-iminoethyl)phenols) possessing two potential minimums. The potentials for proton vibration in the OH and HN tautomers of o-hydroxyaryl ketimines were investigated and anharmonic frequencies were determined. Solvent and substituent effects were analyzed. The energies of the various conformers of the OH and HN tautomers were compared with the related forms of o-hydroxyaryl aldimine.