PAPER CHROMATOGRAPHY OF SOME AMINE HYDROCHLORIDES AND ACETATES IN ACIDIC SOLVENT SYSTEMS

Abstract

The chromatography of piperidine, cyclohexylamine, benzylamine, and morpholine hydrochlorides on unwashed Whatman No. 1 and No. 17 papers in t-butanol: acetic acid: water (2:1:1) leads in each case to partial conversion to the acetate salt, the mobility of which differs from that of the hydrochloride. The interconversion is reduced but is not prevented by the use of acid-washed papers and is increased again when the acid-washed papers are treated with sodium, potassium, calcium, or magnesium acetate prior to chromatography. The salt interconversion is continuous during development of the chromatograms, extended development leading to complete disappearance of the hydrochloride. Quantitative chromatography of piperidine and morpholine hydrochlorides revealed that the extent of salt interconversion is ca. 12% on unwashed and calcium ion washed Whatman No. 17 papers, ca. 6% on sodium ion washed papers, and ca. 1% on acid-washed papers. Piperidinium ions become bound to unwashed, acid-washed, and salt-washed Whatman No. 17 papers during chromatography in aqueous solution just as they do to the hydrogen, sodium, and calcium forms of the carboxylate ion exchanger Amberlite IRC-50 under similar conditions, indicating that a cation exchange mechanism involving carboxyl groups in the paper is responsible for the observed salt interconversion.