On tautomerism of 1,2,4-triazol-3-ones

- F, BeH, NO2, BH2, and N(CH3)2 substituted triazolones were studied at the B3LYP/aug-cc-pVTZ level.
- Only 5-substituted 2,4-dihydro 1,2,4-triazol-3-one form is present in the gas phase and water.
- In contrast, protonation favors complex equilibria between one keto and two hydroxy tautomers.
- Conversion of CO to OH tautomers changes the ring σ- and π-electron population by ca. 0.3 e and −0.3 e.
- Triazolone aromaticity is increased by π-electron acceptors and is decreased by π- and σ-donors.