Tautomere 3‐Acetyltetramsäurederivate – 1H/13C‐NMR‐Untersuchung

Tautomeric 3‐Acetyltetramic Acid Derivatives –1H/13C‐n.m.r.‐Investigation The molecular structure of 1,5,5‐trimethyl‐3‐acetyltetramic acid (I) and its Schiffbases with ethylendiamin (II) and 1,3‐diaminopropan‐2‐ol (III) is described by an equilibrium of four tautomers. The solvent dependence of the equilibrium is attributed to the strength of the intramolecular hydrogen bond. The higher proton affinity of the Schiff‐bases (II and III) in comparison with the ketone (I) should be responsible for the faster equilibration of II and III.