These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Homonuclear versus heteronuclear resonance-assisted hydrogen bonds: tautomerism, aromaticity, and intramolecular hydrogen bonding in heterocyclic systems with different exocyclic proton donor/acceptor.
    Author: Zubatyuk RI, Shishkin OV, Gorb L, Leszczynski J.
    Journal: J Phys Chem A; 2009 Mar 26; 113(12):2943-52. PubMed ID: 19296712.
    Abstract:
    Tautomerism and resonance-assisted hydrogen bonding have been analyzed on the basis of the results of ab initio calculations at the MP2/AUG-cc-pVDZ level of theory for the series of molecules containing different heterocycles connected with resonance spacer and containing different exocyclic proton donor/acceptor atoms. It is demonstrated that the position of tautomeric equilibrium is controlled mainly by two factors: aromaticity of heterocycle, which could be different for two tautomers, and relative proton affinities of two heteroatoms forming a hydrogen bond. Replacement of exocyclic proton donor/acceptor atom results in change of an aromaticity degree of heterocycle leading to alteration of relative stability of tautomers. Comparison of structure and properties of E and Z conformers of molecules demonstrates resonance-assisted character of intramolecular hydrogen bond. Application of the NBO theory reveals that the pi-component of the electron density within resonant spacer plays the primary role for determination of characteristics of hydrogen bond while sigma-skeleton only reflects the pi-polarization. An analysis of strength of intramolecular hydrogen bond using geometrical, energetic, and AIM and NBO parameters indicates that the homonuclear N...H-N hydrogen bond is considerably weaker than heteronuclear N...H-O and N...H-S hydrogen bonds in the case of the XH tautomers.
    [Abstract] [Full Text] [Related] [New Search]