Temperature-variable NMR Study of the keto-enol Tautomerism of Phenylpyruvic Acid

Abstract

The keto-enol tautomerism of phenylpyruvic acid (PPA) has been studied by temperature-variable 9.4 T nuclear magnetic resonance (NMR) spectroscopy. It was found that PPA favored its existence in the enol form in dimethyl sulfoxide (DMSO) solvent, 93.5% of the enol and 6.5% of the keto tautomer was present in DMSO at room temperature. Increasing the temperature increased the percentage of the keto form. The experimental thermodynamic parameters for the tautomerism were successfully obtained from the spectral data.