Aromaticity-Controlled Tautomerism and Resonance-Assisted
Hydrogen Bonding in Heterocyclic Enaminone−Iminoenol Systems
Roman I. Zubatyuk
Yulian M. Volovenko
Oleg V. Shishkin
Leonid Gorb
Jerzy Leszczynski
10.1021/jo0616411.s003
https://acs.figshare.com/articles/journal_contribution/Aromaticity_Controlled_Tautomerism_and_Resonance_Assisted_Hydrogen_Bonding_in_Heterocyclic_Enaminone_Iminoenol_Systems/3029482
The contribution of aromaticity and intramolecular hydrogen bonding to relative stability, for a set of
(1<i>H</i>-azahetero-2-ylidene)-acetaldehyde and 2-azahetero-2-yl-ethanol tautomeric pairs, has been investigated
by means of quantum chemical DFT and ab initio methods up to the MP4(SDTQ)/AUG-cc-pVDZ and
MP2/AUG-cc-pVTZ levels of theory. It is found that the relative energy of the tautomers is governed by
the change in the degree of heterocycle aromaticity upon intramolecular hydrogen transfer. An analysis
of geometrical parameters of a hydrogen-bonded system reveals a clear relationship between the aromaticity
of the heterocycle, the conjugation in a resonant spacer, and the strengths of the intramolecular hydrogen
bonds. This allows the conclusion to be drawn that intramolecular N−H···O and O−H···N hydrogen
bonds formed are found to be resonance-assisted and their strength is dependent on the π-donating/accepting properties of the heterocycle. On the basis of the results of the calculations, a simple model
describing the mechanism of resonance assistance of hydrogen bonding has been suggested.
2007-02-02 00:00:00
heterocycle aromaticity
MP
ab initio methods
intramolecular hydrogen
quantum chemical DFT
resonance assistance
strength
intramolecular hydrogen transfer
intramolecular hydrogen bonds