Abstract

Prototropic tautomerism in 4-quinolone-3-carboxylic acid derivatives has been studied with particular emphasis on the influence of the ring substituents on the equilibrium. The techniques used include UV, H-1-NMR, C-13-NMR (solution) and C-13-NMR CP/MAS (solid state) and semiempirical and ab initio calculations. The pK(a) values of some quinolone derivatives have been determined and correlated with data obtained from semiempirical methods.