Evaluation of the hydrophilic properties of crown ether-ion-pair complexes with alkali metal picrates by their distribution into less-polar diluents.

Cohesive energy densities (C(w,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 K(D,MLA)-vs.-log K(D,L) plots or (ii) intercepts of their plots and from both procedures. Here, K(D,MLA) and K(D,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 C(w,MLA) calculation. The C(w,MLA) values calculated from the two procedures agreed well, and they were proportional to the log(K(D,MLA))(-1) values. From the log K(D,MLA) values for dinitrophenolates and previously-reported values for Na(18C6)A, the hydrophobic property of some pairing anions, A(-), was ordered as F(3)CCO(2)(-) < ReO(4)(-) < MnO(4)(-) < 2,4-dinitrophenolate < 2,6-dinitrophenolate < picrate, and then discussed based on a relation with the log K(ex) values, where K(ex) shows the extraction constant (mol(-2) dm(6) unit) for Na(18C6)A into 1,2-dichloroethane.