The Influence of Alkyl Chain Length on Stability Constants of Zn(II) Complexes with 1‐Alkylimidazoles in Aqueous Solutions and Their Partition Between Aqueous Phase and Organic Solvent

The extraction of Zn(II) complexes with nine derivatives of 1‐alkylimidazoles (R from C4H9– to C14H29–) from aqueous solutions [I = 0.5 (KNO3) at 25°C] with toluene, p‐xylene, dichloromethane, and 2‐ethyl‐1‐hexanol was investigated. The extraction curves for all four solvents were found to displace towards lower pH values with increasing alkyl chain length. Stability constants of the complexes formed in the aqueous phase, β n , were determined as well as partition constants, P n , of the extracted species. With increasing alkyl chain length, both the stability constants and the partition coefficients of the complexes have been found to increase. With the more soluble 1‐alkylimidazoles, pseudo‐tetrahedral together with pseudo‐octahedral complexes were formed at the second or third complexation steps. The appearance of configurational equilibria has been found to be dependent on the nature of the solvent used. In this respect, dichloromethane and 2‐ethyl‐1‐hexanol were more favorable than toluene and p‐xylene.