“…The tautomerism of these small molecules has been studied theoretically many times with an increasing level of theoretical calculations. The values in kJ·mol –1 (method) with regard to the most stable one, 1 H ‐1,2,4‐triazole, 3a , are in chronological order: 20.9 (INDO), 25 28.0 (RHF/6‐31G[d]//RHF/6‐31G), 26 26.3 (RHF/6‐31G(d,p)//RHF/3‐21G) + ZPE + MP2], 27 30.1 [MP2/6‐31G(d)//RHF/6‐31G(d)], 28 36.0 (MINDO/3), 29 29.8 [Becke3P86/6‐311G(d,p)], 29 28.9 [RHF/6‐311G(d,p)], 30 28.8 [B3LYP/6‐31G(d)], 31 26.7 [MP2‐(fc)/6‐311 + G(d,p)], 32 28.5 [B3LYP/6‐311++G(d,p)], 33 30.1 [B3PW91/6‐311++G(d,p)], and 26.0 [B3LYP/6‐311++g(d,p)], 34 26.0 (CBS‐4 M), 35 24.9 (CBS‐QB3) 35 and 26.1 CCSD(T)/cc‐pCVTZ 35 …”