Nuclear magnetic resonance studyes of triazoles. I. Tautomerism of 1,2,4-triazole

Five‐Membered Heterocycles with Three Heteroatoms: Triazoles

“…The pK a of the protonated species is 2.19 and the weakly basic nature allows electrophilic attack at the N4 position in 1-substituted-1,2,4-triazoles. The 1 H NMR spectrum of the parent 1,2,4-triazole in HMPT is temperature dependent; the H3 and H5 protons show one broad singlet at slightly above or below room temperature due to the rapid proton exchange between the tautomeric forms ( Table 12.16) [192]. However, at À34 C, the H3 protons and H5 protons are observed separately.…”

Gas-Phase Tautomerism in the Triazoles and Tetrazoles: A Study by Photoelectron Spectroscopy and ab Initio Molecular Orbital Calculations

“…The spectra obtained in the latter three cases relate to tautomeric mixtures, namely 4a5a%8a, 6a%9a, and it had been assumed that the tautomer present in the gas phase would be the same as in the solid state or solution, there being no evidence to the contrary; thus we assigned the spectra on the basis of 4a, 5a and 6 a rather than 7 a, 8 a or 9a, respectively [2,3,4].…”

The structure of azines derived from C‐formyl‐1H‐imidazoles in solution and in the solid state: tautomerism, configurational and conformational studies

“…HMPA was introduced in 1968 by Creagh and Truitt to study by 1 H NMR the tautomerism of 1 H ‐1,2,4‐triazole (see also) and then in 1977 extended by Chenon et al . to 1 H ‐pyrazoles and 13 C NMR.…”

“…HMPA was introduced in 1968 by Creagh and Truitt [45] to study by 1 H NMR the tautomerism of 1H-1,2,4-triazole (see also [46] ) and then in 1977 extended by Chenon et al [47] to 1Hpyrazoles and 13 C NMR. Our first use of this solvent was reported in 1991 and concerns the use of 13 C NMR spectroscopy to study the tautomerism of 1H-pyrazoles [48] followed by a 1 H, 13 C, and 15 N NMR study of other 1H-pyrazoles.…”