engleski

Substituend, temperature, and solvent effects on keto-enol equilibrium in some symmetrical pentane-1,3,5-triones. Nuclear magnetic resonance and theoretical studies

Keto-enol tautomeric equilibrium in several beta-triketones has been investigated using NMR spectroscopy and theoretical methods. The equilibrium involves two slow and two fast enolization processes in solution. At room temperature and in solvents of low polarity the predominant tautomeric species is the dienol form. However, the equilibrium is significantly shifted to more polar triketo form on going from the room temperature up to 140 °C and by using solvents with higher polarity. Structures and stabilities of both long- and short-lived tautomeric forms, as well as transition-state structures and barrier heights of enolization processes were calculated using semiempirical and density functional quantum chemical methods.

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