Partition and complex formation of alkali metal ion with long chain poly(oxyethylene) derivatives in 1,2-dichloroethane

Abstract

The partition and dissociation equilibria of the ion pair of alkali metal ion (M⁺) complexes of long chain polyoxyethylene alkylphenyl ethers, Tr–X (the mean number of oxyethylene units, =10–43), with picrate ion (pic^-) in 1,2-dichloroethane were studied and compared with those of the short chain poly(oxyethylene) compounds, DEOn (the number of oxyethylene units, n=4, 6 and 8). The distribution constant of the ion pair, SM⁺·pic^- (S: Tr–X and DEOn), increases in the order of Li⁺<Na⁺<K⁺≈Cs⁺ and does not show a smooth correlation with the number of oxyethylene units of S. The dissociation constants of the ion pair of long chain complexes are hardly changed by the change in the metal ion and the number of oxyethylene units. The complex formation constants of alkali metal ions with Tr–X were evaluated by using the partition data of alkali metal picrates. The complex formation constant increases in the order Li⁺<Na⁺≈K⁺>Cs⁺ and smoothly increases as the number of oxyethylene units increases.The increments of formation constants are interpreted by the increase in the number of oxygen atoms available for coordination to metal ion. The distribution constants of dinuclear complexes, Tr–X(M⁺)₂·(pic^-)₂, were also determined.