Simple pyrimidines. XVII. The effect of 4'(6')-substituents on the ionization of 2-(Pyrimidin-2'-yl)acetic acid

Abstract

The synthesis of a series of 4'-mono- and 4',6'-di-substituted derivatives of 2-(pyrimidin-2'-yl)acetic acid (1a) and the corresponding methyl esters is described. When allowance is made for the proportion of zwitterion present, the modified anionic pK_a values of the monosubstituted acids show a reasonable correlation with an almost equal blend of the substituent parameters σ_I and σ_R⁺. The disubstituted acids show no such discernible correlation.