Baranac-Stojanović Marija, Aleksić Jovana, Stojanović Milovan
University of Belgrade - Faculty of Chemistry, Studentski trg 12-16, P. O. Box 158, 11000 Belgrade, Serbia.
University of Belgrade - Institute of Chemistry, Technology and Metallurgy - Center for Chemistry, Njegoševa 12, P. O. Box 473, 11000 Belgrade, Serbia.
Org Biomol Chem. 2023 Dec 20;22(1):144-158. doi: 10.1039/d3ob01588b.
Computational investigation at the BHandHLYP/6-311+G(d,p) level of theory of the gas-phase tautomerism of 2- and 4-pyridones confirmed the slight prevalence of lactim in the case of the former, but its dominance in the case of the latter, as shown previously. Examination of aromaticity by using HOMA, EDDB, NBOdel, NICS and AICD led to the conclusion that tautomerization of 4-pyridone results in greater aromaticity gain. It is also driven by the Pauli repulsion relief, which was revealed by the tautomerization energy decomposition analysis. By contrast, in the case of 2-pyridone, lactim is favoured by orbital and electrostatic interactions and disfavoured by the Pauli repulsion. Aromaticity gain in this case is smaller. The position of the tautomeric equilibrium can be modulated by substituent inductive effects (Cl and F), inductive and resonance effects (NH and NO), hydrogen bonding (NO), and medium polarity, the increase of which increases lactam population.
在BHandHLYP/6 - 311 + G(d,p)理论水平下对2 - 吡啶酮和4 - 吡啶酮气相互变异构进行的计算研究证实，前者中烯醇式略微占优，而后者中则是酮式占主导，如先前所示。通过使用HOMA、EDDB、NBOdel、NICS和AICD对芳香性进行考察得出结论，4 - 吡啶酮的互变异构导致更大的芳香性增加。它还受到泡利排斥缓解的驱动，这是通过互变异构能量分解分析揭示的。相比之下，在2 - 吡啶酮的情况下，烯醇式受轨道和静电相互作用的青睐，而受泡利排斥的不利影响。在这种情况下芳香性增加较小。互变异构平衡的位置可以通过取代基的诱导效应（Cl和F）、诱导和共振效应（NH和NO）、氢键（NO）以及介质极性来调节，介质极性的增加会使内酰胺形式的比例增加。
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