Analytical Sciences

Abstract − Analytical Sciences, 25(4), 563 (2009).

Evaluation of the Hydrophilic Properties of Crown Ether-ion-pair Complexes with Alkali Metal Picrates by Their Distribution into Less-polar Diluents
Yoshihiro KUDO, Shoichi KATSUTA, and Yasuyuki TAKEDA
Graduate School of Science, Chiba University, Chiba 263-8522, Japan
Cohesive energy densities (Cw,MLA/J cm-3) for ion-pair complexes (MLA: M+ = Li+ to Cs+; w: water) with six crown ethers (L), such as 18-crown-6 ether (18C6), benzo-18C6, and dibenzo-24-crown-8 one, and A- = picrate were calculated at 298 K by a procedure that uses either (i) an equation rearranged from that underlying log KD,MLA-vs.-log KD,L plots or (ii) intercepts of their plots and from both procedures. Here, KD,MLA and KD,L denote the distribution constants of MLA and L from w into a diluent, respectively. As additional MLA, Na(18C6)(2,4-dinitrophenolate) and Na(18C6)(2,6-dinitrophenolate) were employed for the present Cw,MLA calculation. The Cw,MLA values calculated from the two procedures agreed well, and they were proportional to the log(KD,MLA)-1 values. From the log KD,MLA values for dinitrophenolates and previously-reported values for Na(18C6)A, the hydrophobic property of some pairing anions, A-, was ordered as F3CCO2- < ReO4- < MnO4- < 2,4-dinitrophenolate < 2,6-dinitrophenolate < picrate, and then discussed based on a relation with the log Kex values, where Kex shows the extraction constant (mol-2 dm6 unit) for Na(18C6)A into 1,2-dichloroethane.