DFT (B3PW91/6-311þþG**), ab initio (HF/6-311þþG**), and single point CCSD(T)/6-311þþG**//B3PW91/6311þþG** calculations were performed to investigate the stability and tautomerism of the C5-substituted 1,2,3-triazoles. Three different tautomers are possible for the substituted 1,2,3-triazoles: N1–H, N2–H, and N3–H. For all the substituents applied, the most stable is the N2–H tautomer. Out of th...