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<p>An attempt is made for the first time by our laboratory to apply the Hammett and Taft equations to a five-membered ring system with four nitrogens as heteroatoms, viz., tetrazole, to identify the aqueous medium 1H and 2H tautomers. For this purpose, experimentally determined aqueous medium p<i>K</i><sub>a</sub> values of N(1)H-acidities of fifteen 5-X-1, 2, 3, 4-tetrazoles. DFT/B 3LYP method at the 6–31G* level calculated dipole moments of seven 1H and 2H tautomers of 5-X-1, 2, 3, 4-tetrazoles have been correlated with Hammett <i>σ</i><sub>para</sub> and <i>σ</i><sub>meta</sub>, and Taft <i>σ</i>*<sub>ortho</sub> values. Good correlations are obtained. The promising response of more abundant and more polar 1H tautomer with less susceptibility (<i>ρ</i>* = −1.38 in p<i>K</i><sub>a</sub> correlations and <i>ρ</i>* = −0.55 in dipole moments correlation) to Taft equation and less abundant and less polar 2H tautomer with more susceptibility (<i>ρ</i><sub>para</sub> = 6.56, <i>ρ</i><sub>meta</sub> = 7.79 in p<i>K</i><sub>a</sub> correlations, and <i>ρ</i><sub>para</sub> = 2.69, <i>ρ</i><sub>meta</sub> = 3.26 in dipole moments correlation) to Hammett equation of the tetrazole is well distinguished. Thus, it applies the reactivity-selectivity principle to a chemical property like the ionization of NH of tetrazole and to a physical property like dipole moment for the first time. Therefore, a way has been found to achieve the equilibrium identification of 1H and 2H tautomers without using any expensive and time-consuming experimental techniques.</p>

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Identifying 1H/2H Tetrazole Tautomers via LFER: A Chemical Education Perspective

  • 期刊论文

  • 发表日期：

    2025年9月1日

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  • Sanjeev Rachuru,
  • Ankamma Kukkadapu,
  • V. Jagannadham

摘要

An attempt is made for the first time by our laboratory to apply the Hammett and Taft equations to a five-membered ring system with four nitrogens as heteroatoms, viz., tetrazole, to identify the aqueous medium 1H and 2H tautomers. For this purpose, experimentally determined aqueous medium pKa values of N(1)H-acidities of fifteen 5-X-1, 2, 3, 4-tetrazoles. DFT/B 3LYP method at the 6–31G* level calculated dipole moments of seven 1H and 2H tautomers of 5-X-1, 2, 3, 4-tetrazoles have been correlated with Hammett σpara and σmeta, and Taft σ*ortho values. Good correlations are obtained. The promising response of more abundant and more polar 1H tautomer with less susceptibility (ρ* = −1.38 in pKa correlations and ρ* = −0.55 in dipole moments correlation) to Taft equation and less abundant and less polar 2H tautomer with more susceptibility (ρpara = 6.56, ρmeta = 7.79 in pKa correlations, and ρpara = 2.69, ρmeta = 3.26 in dipole moments correlation) to Hammett equation of the tetrazole is well distinguished. Thus, it applies the reactivity-selectivity principle to a chemical property like the ionization of NH of tetrazole and to a physical property like dipole moment for the first time. Therefore, a way has been found to achieve the equilibrium identification of 1H and 2H tautomers without using any expensive and time-consuming experimental techniques.