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

Abstract

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).