Tautomerization tendencies of 2-acetylcycloalkanones, 2-acetyl-1,3-cycloalkanediones, and cyclic β-keto esters of five- and six-membered rings

Abstract

NMR and kinetics studies of the tautomeric equilibrium of 2-acetylcycloalkanones, 2-acetyl-1,3-cycloalkanediones, and methyl 2-oxocycloalkanecarboxylates of five- and six-membered rings have been carried out. By comparing 1H NMR and 13C NMR spectra recorded in D2O–DOCD3 and CDCl3, with those results derived using a bromination kinetic procedure in dilute aqueous solution, information concerning tautomeric interconversion is provided. Some discussions considering ionisation equilibria and rate constants involved have also been considered. Solvent and concentration effects on keto-enol equilibria have also been discussed.Key words: 2-acetylcycloalkanones, 2-acetyl-1,3-cycloalkanediones, methyl 2-oxocycloalkanecarboxylates, equilibrium, tautomerization, ionization.