Zum Einfluß der Alkylkette auf Protolyse,Komplexbildung und Extraktionseigenschaften N-substituierter 2-(o-Hydroxyphenyl)-Δ2-imidazoline

Influence of the Alkyl Chain on Protolysis, Complex Formation, and Extraction Properties of N-Substituted 2-(Δ²-Imidazolin-2-yl)-phenols N-substituted 2-(Δ²-imidazolin-2-yl)-phenols RNNOH may be used as extractants of copper(II) from acidic solutions. In an aqueous phase they are existent as betains \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm R}\mathop {\rm N}\limits^ \oplus {\rm HNO}^ \ominus $\end{document} ( IIa ). Solvents with lower dielectricity constants (dioxane-water-mixtures) favour the neutral acid RNNOH ( IIb ) a tautomer of IIa . The protonation of IIa or IIb proceeds in a weakly acidic solution. Therefore, at 3 ≤ pH ≤ 4 which is favourable for copper(II) extraction, the extractants exist as the cations RNHNOH]⁺. The octyl compound OcNNOH from such a solution is extracted by chloroform, less effective by toluene, as an ion pair \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm Oc}\mathop {\rm N}\limits^ \oplus {\rm HNOH]X} $\end{document}. The distribution coefficient increases in the order HSO₄^? < NO₃^? < ClO₄^? which is well-known for quaternary ammonium salts. The affinity of the ion pairs, which are derived from the butyl compound BuNNOH, to organic solvents is very weak independently of the anion. For solubility reasons a study of the formation of the trans-planar copper(II) chelates Cu(RNNO)₂ is possible only in dioxane-water mixtures. Because of lg K₁ ≥ lg k₂ + 2 the stability regions of Cu(RNNO)⁺ and CU(RNNO)₂ are clearly separated. The distribution coefficients of Cu(RNNO)₂ increase with the length of R exceeding that of the free ligand by one power of ten and more.