Heterocyclic Azomethine Compounds and Their Reduction Products as Analytical Reagents. I. Syntheses and Acid Dissociation Constants of Picolinaldehyde 2-Hydroxyanil and Its Derivatives and Their Reactions with Metal Ions

Abstract

Abstract Picolinaldehyde 2-hydroxyanil and its methyl, chloro and nitro derivatives at the 5-position of benzene nucleus were synthesized for the purpose of investigating their applicability as an analytical reagent. The acid dissociation constants were determined by means of potentiometric titration in aqueous dioxane of various concentrations. It was found that the basicity of donor atoms of the parent compound increases with the introduction of a methyl group and decreases with that of a chloro or nitro group. The three compounds other than the nitro derivative are light-colored and react with many divalent metal ions in slightly basic media to form strongly colored chelates, which can be extracted into organic solvents such as partially halogenated hydrocarbons. The distribution coefficients of the three compounds between chloroform and water were also determined spectrophotometrically, that of the chloro derivative being the largest.