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Journal of Applied Sciences
  Year: 2008 | Volume: 8 | Issue: 15 | Page No.: 2659-2668
DOI: 10.3923/jas.2008.2659.2668
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Effect of Different Substituents on the Amino-Oxo/Amino-Hydroxy Cytosine Tautomeric System
Hamzeh S.M. Al-Omari

Amino-oxo cytosine and amino-hydroxy cytosine tautomeric system was studied by employing MNDO semi-empirical method of calculations. The amino-hydroxy structure was found to be energetically favorable over amino-oxo form of cytosine as indicated by the calculated heat of formation and Gibbs free energy. The substitution of F, OH, CN, NH2, BH2 and CH3 at carbon 6-position was studied. All the substituents are found to affect the geometrical parameters of the substituted structures. The equilibria between the substituted amino-oxo and amino-hydroxy cytosines were studied by the Gibbs free energy change and by isodesmic reactions. The calculations were performed at 25C. It is found that all substituents push the equilibria in the forward direction compared to the unsubstituted tautomeric pairs except in the case of BH2 substituent where the equilibrium becomes slightly less favourable in the forward direction.
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How to cite this article:

Hamzeh S.M. Al-Omari , 2008. Effect of Different Substituents on the Amino-Oxo/Amino-Hydroxy Cytosine Tautomeric System. Journal of Applied Sciences, 8: 2659-2668.

DOI: 10.3923/jas.2008.2659.2668








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