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Journal of Solution Chemistry

, Volume 41, Issue 5, pp 864–878 | Cite as

Density Functional Theory Study of Hypoxanthine Tautomerism in Both the Isolated State and a Modeled-Ideal Aqueous Solution at Several Heterocyclic Protonation Levels

  • María Eugenia Costas
  • Rodolfo Acevedo-Chávez
Article

Abstract

In order to advance the knowledge of prototropic tautomerism from the physicochemical point of view, the purine derivative hypoxanthine has been selected and studied. The overall purpose has been to explore thermodynamic aspects of the heterocycle tautomerism under the influence of both its protonation level and the surrounding dielectric constant. A Density Functional Theory study (at the B3LYP/6-31++G** level) was performed, in which the energetic and thermodynamic stabilities, the electric dipole moment values, the tautomeric equilibrium constants and the tautomeric populations were obtained for several hypoxanthine tautomers under systematically modified heterocyclic protonation levels, considering both isolated and ideal aqueous solution states. Among the interesting results obtained are changes in the tautomeric populations for several heterocyclic protonation states and with the increase of the dielectric constant. Several of the predictions made for an aqueous solution show good agreement with recently reported experimental conclusions. Also, the ionizable groups that contribute to the different hypoxanthine ionization steps in the main tautomers have been established. These and other related results are presented and discussed. Finally, the confidence developed in the predicted tautomeric populations in a modeled-ideal aqueous solution allows us to propose that the methodology applied here can be used for the study of prototropic tautomerism in heterocycles belonging to this class, particularly when the experimental work is challenging in both performance and physicochemical data analysis.

Keywords

Hypoxanthine Tautomerism Protonic dissociations Theoretical calculations Electron–donor sites basicities Density functional theory Acid/base properties 

Notes

Acknowledgements

The authors are indebted to the Dirección General de Asuntos del Personal Académico-Universidad Nacional Autónoma de México (IN101208) for financial support.

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Copyright information

© Springer Science+Business Media, LLC 2012

Authors and Affiliations

  • María Eugenia Costas
    • 1
  • Rodolfo Acevedo-Chávez
    • 1
  1. 1.Departamento de Fisicoquímica, Facultad de QuímicaUniversidad Nacional Autónoma de MéxicoMexico D.F.Mexico

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