C-13 NMR Spectra of Barbituric Acid Derivatives

Abstract

Carbon-13 nuclear magnetic resonance (NMR) spectra of nine kinds of mono-substituted barbituric acid derivatives were measured. Two conclusions were obtained from the analysis of carbon-13 NMR spectra. (1) The so-called additive law is applicable to chemical shifts of the carbon at 5-position. (2) There is a correlation between chemical shifts of the carbon at 5-position and pK_a, values, except in barbituric acid and 5-methylbarbituric acid.