Extraction of aliphatic monocarboxylic acids with high molecular weight amine

Abstract

Chloro-substituted acetic acids were extracted from their dilute aqueous solutions into organic solvents containing tri-n-octylamine, by amounts considerably greater than those expected by sto ichiometry. Generally, 3 moles of the acids were extracted by one mole of tri-n-octylamine. Various factors on the formation of an ion pair and of complexes with excess acids were also examined. Extractions of acetic acid, propionic acid and butyric acid, however, were dependent largely on the number of alkyl carbons and hence partly on their solubilities in the solvent.
The NMR and IR spectra in carbon tetrachloride indicated that tri-n-octylammonium ion and dichloroacetate anion formed an ion pair in the range R< 1, and, in higher acid concentrations, hydrogen bond complexes were formed between these ion pairs and acid molecules, which would result in a weakening of the ion pair bond. The number of acid molecules in the complexes did not exceed three, since further interactions seemed to be very weak.