A computational study of gas-phase acidity and basicity of azulene-based uracil analogue

  • Safinaz H. El-DemerdashEmail author
  • Shaimaa F. Gad
Original Research


In this paper, we suggest a computational scheme for the theoretical estimation of gas-phase acidity and basicity of azulene-based uracil analogue. The proton affinities (PAs) of the two oxygen and of the two nitrogen atoms and the deprotonation energies (DPEs) of the two NH and of the two OH bonds of azulene-based uracil analogue isomers are calculated by density functional theory (DFT) using the 6-31+G(d,p) basis set and by high ab initio MO theory (CBS-QB3) method. The PAs of the oxygen and nitrogen atoms of 13 tautomers range from 197.9 to 230.4 kcal/mol and the DPEs of the OH and NH groups from 300 to 342.3 kcal/mol. The proton affinities of di-keto form AZU1 followed the order O9 (N1 site), O9 (N3 site), O11 (N3 site), and O11 (H13 site).


Tautomerism Uracil analogue Azulene CBS-QB3 Proton affinity Deprotonation enthalpy 


Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflicts of interest.

Supplementary material

11224_2019_1408_MOESM1_ESM.docx (647 kb)
ESM 1 Supplementary data associated with this article can be found in the online version (DOCX 646 kb)


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Authors and Affiliations

  1. 1.Chemistry Department, Faculty of ScienceMenoufia UniversityShebin El-KomEgypt
  2. 2.Chemistry Department, Faculty of ScienceKafr El-sheikh UniversityKafr El-SheikhEgypt

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