Study of Tautomerism by Nuclear Magnetic Resonance Spectroscopy

Molecular Theory of Solvent Effect on Keto−Enol Tautomers of Formamide in Aprotic Solvents: RISM-SCF Approach

“…For the keto−enol equilibria, the keto tautomer is stabilized in comparison with the enol one, which is consistent with the larger dipole moment of the keto tautomer than the enol one. This is in qualitative accord with the experimental findings on similar tautomeric systems. , …”

“…This is in qualitative accord with the experimental findings on similar tautomeric systems. 16,18 (b) SolVation Free Energy Analyses. In Table 4, the solvation free energies of the keto and enol form of formamide in aprotic solvents are shown.…”

“…Many examples of the solvent effects on chemical equilibria and reactions have been observed. Among them, the solvent effect on the keto−enol tautomerism has been extensively studied. , Experimentally, it is known that the keto−enol equilibrium constants change depending on the solvent polarity in solution. − Theoretical studies of the specific systems such as 2-pyridone , and formamide ,, have been reported, but in most of them, the solvent was treated as a dielectric continuum and little information was obtained on the structure of solvents around the solute. In these studies, the solvation free energy has been interpreted in relation to the dielectric constants, which are macroscopic properties of solvents and could not be treated from the viewpoint of a microscopic picture.…”

“…Among them, the solvent effect on the keto-enol tautomerism has been extensively studied. 15,16 Experimentally, it is known that the keto-enol equilibrium constants change depending on the solvent polarity in solution. [17][18][19][20] Theoretical studies of the specific systems such as 2-pyridone 1,21 and formamide 1,21,22 have been reported, but in most of them, the solvent was treated as a dielectric continuum and little information was obtained on the structure of solvents around the solute.…”

Synthesis, structure and solvatochromism of new 5-(4-substituted phenylazo)-4-(4-substituted phenyl)-6-hydroxy-3-cyano-2-pyridones

“…Solvent effects similar to those described for the keto/enol equilibrium can also be found for other tautomerisms, e.g. lactam/lactim, azo/hydrazone, ring/chain equilibria, etc [144,145] One of the classic studies of lactam/lactim tautomerisms is the determination of…”