Effect of Alkyl Chain Length on the Extraction of Copper(II) Complexes with 1‐Alkyl‐2‐Methylimidazoles

Abstract

By using the liquid‐liquid partition method, the formation of Cu(II) complexes with 1‐alkyl‐2‐methylimidazoles (where alkyl=isobutyl, pentyl, isopentyl, hexyl, octyl, decyl, and dodecyl) has been studied at 25°C and at fixed ionic strength of the aqueous phase (I=0.5; (HL)NO₃, KNO₃). The complexes were extracted with 2‐ethyl‐1‐hexanol, dichloromethane, trichloromethane and, in one system only, toluene. Stability constants of the complexes in aqueous solution as well as partition constants of the extractable species were determined. It has been shown that the stability constants are invariable and do not depend on the 1‐alkyl chain length. The constants were smaller than those of the previously studied Cu(II) – 1‐alkylimidazole complexes owing to the steric effect of the methyl group at position 2. The partition constants of the complexes incereased with increasing alkyl chain length. Branched 1‐alkyl substituents (isobutyl, isopentyl) suppressed both stability constants and the partition constants of the complexes.

Keywords:

• Solvent extraction
• Cu(II) complexes
• 1‐alkyl‐2‐methylimidazole
• stability constants
• partition constants