The energetic stability and structural and electronic properties of all the ketonic and enolic tautomers of neutral hypoxanthine are studied at the level of density functional theory, We also study the influence of temperature on the tautomeric equilibria and the IR vibrational spectrum of this heterocycle in the gas phase in terms of the contributions of several tautomers. We found that the two N(1)-H ketonic tautomers of hypoxanthine are the energetically most stable ones and represent the main contribution to the experimental IR spectrum. The calculated properties and the potential chemical behavior suggested for hypoxanthine from the theoretical study are in remarkable agreement with the experimental data reported up to date.