Analytical Sciences


Abstract − Analytical Sciences, 24(8), 999 (2008).

Evaluation of the Hydrophilic Property of Sodium Ion-pair Complexes with 3m-Crown-m Ethers (m = 5, 6) and Their Benzo-derivatives by Solvent Extraction
Yoshihiro KUDO,* Ryo FUJIHARA,** Toshiaki OHTAKE,*** Shoichi KATSUTA,* and Yasuyuki TAKEDA*
*Graduate School of Science, Chiba University, Chiba 263-8522, Japan
**Graduate School of Science and Technology, Chiba University, Chiba 263-8522, Japan
***Department of Chemistry, Faculty of Science, Chiba University, Chiba 263-8522, Japan
The ion-pair formation constants {Kj0: j = MA (metal salt), MLA} of NaO2CCF3 (Na+tfa-) and its ion-pair complexes (MLA) in water (w) were determined potentiometrically at 25°C and an ionic strength (I) of zero. 15-Crown-5 (15C5), 18-crown-6 ethers (18C6), and their mono-benzo derivatives were used as crown ethers (L). The extraction of Natfa by these four L from w into 1,2-dichloroethane was done at 25°C, and then the extraction constants (Kex) for NaLtfa were calculated by using the Kj values, which were estimated from the corresponding Kj0 ones at I of the w-phases, and other equilibrium constants. Also, the distribution constants (KD,MLA) of NaLtfa between the two phases were obtained from a thermodynamic cycle expressing Kex. An interaction of w-molecules with NaLA was considered using a relation of log KD,MLA with log KD,L, derived from the Scatchard-Hildebrand equation, where KD,L denotes the distribution constant of L between the two phases. The interaction increased in the order of NaL (picrate) < free L ≤ NaLMO4 (M = Mn, Re) < NaLtfa for L = 15C5 and 18C6.