Linear free energy relationship in thin layer chromatography of 5-arylidenebarbiturates

Summary Among 33 investigated 5-arylidenebarbiturates (I) and their N,N-dimethyl analogs (II) containing different substituents in the phenyl ring, 14 are new derivatives. Substituent effects of the phenyl ring on the ability of adsorption on silica gel were observed by TLC. The significant correlations between the R_M values and or ⁺ substient constants were found for both ortho-substituted derivatives of series I and N,N-di-methyl derivatives of series II. The mechanism of adsorption on the silica gel in relationships to our previous studies on barbituric acid derivatives is discussed.Part of this work has been presented at the Budapest Chromatography Conference, June 1–3, 1983.