SOLVENT-EXTRACTION OF 8-QUINOLINOLATO IRON(III) WITH THE AID OF VARIOUS PHENOLS AS HYDROGEN-BONDING DONORS

Effect of various phenols (ArOH) on the solvent extraction of iron(III) with 8-quinolinol (HQ) has been investigated. Greatly enhanced extraction is found in the presence of ArOH, e.g., the distribution ratio of iron(III) with HQ in carbon tetrachloride is increased 200,000-fold by 0.10M 3,5-dichlorophenol. From extraction equilibrium analysis, the enhanced extraction has been ascribed to the formation of association complexes of neutral iron(III) 8-quinolinolate (FeQ3) with ArOH as FeQ3.nArOH (n = 1, 2, 3) in the organic phase, and the association constants (beta(ass,n)) have been determined. A linear relation is observed between logarithmic values of beta(ass,n) and the acid-dissociation constant of ArOH. Existence of the hydrogen bond between FeQ3 and ArOH is clearly shown by infrared spectroscopy.