Abstract
Individual distribution constants (KD,A) of picrate ion (Pic−) and extraction constants (Kex±) of NaPic by some crown ethers (L) into benzene (Bz) at 25°C were calculated from data reported previously. These constants were defined asKD,Pic=Pic-o/[Pic-]andKex±=NaL+oPic-o/(Na+Lo[Pic-]), respectively. Here, the subscript “o” denotes an organic (o) phase and practically o = Bz. 15-Crown-5 ether (15C5), 18-crown-6 one (18C6), and their monobenzo (B) derivatives (B15C5 and B18C6) were selected as L. Interfacial equilibrium-potential differences (Δϕeq) at extraction were estimated at 298 K. A plot oflogKex±versus-Δϕeqfor the four L extraction systems gave a straight line with slope = 84 V−1. This slope was compared with those, reported before, of the dichloromethane (DCM), 1,2-dichloroethane (DCE), and nitrobenzene (NB) extraction systems. The slopes of the regression lines were in the order NB < DCM ≤ DCE < Bz. Also, the individual distribution constants of the complex ionNaL+and an ion-pair complex (NaL+Pic-) into Bz phase were calculated from the above extraction data. At least, a comparison between these values suggests that Bz molecules mainly interact withNaL+moiety ofNaL+Pic-.
Highlights
A presence of interfacial equilibrium-potential differences (Δφeq) at extraction processes with polar diluents, such as dichloromethane (DCM), 1,2-dichloroethene (DCE), and nitrobenzene (NB), has been clarified [1, 2]
Individual distribution constants of the ion-pair complexes NaL+Pic− and the complex ions (NaL+), which constitute parts of the complexes, into the four diluents were estimated from the above results and their properties for solute-solvent interaction were discussed
In the analysis of an overall extraction equilibrium, the following component equilibria were considered [2, 16]: L LBz (the equilibrium constant for this equilibrium: KD,L; sNNeaaeLLS+Peicc+tBizoP(niKc3D.5,N)a;LNPNicaa;+LseP+eicLSe(cKt1io; Nnsea3eL.5+S);e(NcKtaiNoLanLP;i3cs.eB5ze);SNecaNtLioaPLni+c3B.z5+); picrate ion (Pic−)Bz (K1,Bz−1; see Section 3.2); and Na+ + Pic− NaPic. In addition to these equilibria, one can understand the presence of other component equilibria: NaL+ NaL+Bz (KD,NaL; see Section 3.2 and Table 1) and Pic− Pic−Bz (KD,Pic; see Section 1 and Table 1)
Summary
A presence of interfacial equilibrium-potential differences (Δφeq) at extraction processes with polar diluents, such as dichloromethane (DCM), 1,2-dichloroethene (DCE), and nitrobenzene (NB), has been clarified [1, 2]. Alkaline-earth metal (Ca-Ba) picrates [1] into NB In these studies [1, 2], an individual distribution constant (KD,A) of a pairing anion (A−), such as picrate ion (Pic−), has been determined in the course of Kex determination. Liquid/liquid interfaces had not been reported, except for our studies [1,2,3] and a description [11] with respect to the distribution of a simple salt, such as Bu4NBr. In the present paper, selecting benzene (Bz) as the representative less-polar diluent, we determined from available extraction data [12,13,14,15] Δφeq values at the Bz/w interface. Individual distribution constants of the ion-pair complexes NaL+Pic− and the complex ions (NaL+), which constitute parts of the complexes, into the four diluents were estimated from the above results and their properties for solute-solvent interaction were discussed
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