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E-Journal of Chemistry
Volume 5 (2008), Issue 4, Pages 884-893

Tautomerism of 5-Methyl Imidazolidine Thio Derivatives in the Gas Phase: A Density Functional Study

Zaki S. Safi1 and Fakhr M. Abu-Awwad2

1Department of Chemistry, Al Azhar University-Gaza, Gaza City, Palestine
2Department of Chemistry, The Islamic University of Gaza, Gaza City, Palestine

Received 11 December 2007; Revised 29 January 2008; Accepted 13 February 2008

Copyright © 2008 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Relative tautomerisation energies, enthalpies, entropies, Gibbs free energies, and dipole moments for 5-methyl-2,4-dioxo-imidazolidine and its thio analogous have been studied in the gas phase using hybrid density functional at the B3LYP level of theory using 6-31(d) and 6-311+(2df,2p) basis sets with full geometry optimization. A comparative investigation of their energies revealed that the keto form of the compound is the predominant tautomer with a very high tautomeric energy barrier. The findings conclude that the intramolecular prototropic tautomerisation process is thermodynamically unfavored.