Paper Chromatographic Separation of the Isomeric Pyridinecarboxylic Acids

Abstract

IN the course of study on the synthesis of the hydrazide of isonicotinic acid, starting with ‘50-picoline’, I realized the desirability of providing a control method to follow the separation of the isomeric pyridinecarboxylic acids. Paper chromatography using n-butanol–methanol, a system suggested by the very different solubilities of the acids in methanol and water, has been shown to be very efficient for the separation of the three isomers. The substances used in this experiment were the α-, β- and γ-pyridinecarboxylic acids, a mixture of all three, and the mixture obtained by oxidation of ‘50-picoline’ with potassium permanganate. The solvent used for the development of the substances, as shown in the accompanying figure, was n-butanol–methanol containing 35 per cent water by volume at 20° C. The paper used was Tōyō qualitative filter paper No. 3, 2/40 cm., and the usual ascending method was carried out in a thermostat (18°–20° C).