Extraction of sodium picrate by 3 m -Crown- m ethers and their monobenzo derivatives (m = 5,6) into benzene: Estimation of their equilibrium-potential differences at the less-polar diluent/water interface by an extraction method

Individual distribution constants (k d,a) of picrate ion (pic-) and extraction constants (k e x ±) of napic by some crown ethers (l) into benzene (bz) at 25°c were calculated from data reported previously. these constants were defined as k d,p i c = p i c - o / [ p i c - ] and k e x ± = n a l + o p i c - o / (n a + l o [ p i c - ]),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 (δ φ e q) at extraction were estimated at 298 k. a plot of log k e x ± versus - δ φ e q for 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 ion n a l + and an ion-pair complex (n a l + p i c -) into bz phase were calculated from the above extraction data. at least,a comparison between these values suggests that bz molecules mainly interact with n a l + moiety of n a l + p i c -. © 2016 yoshihiro kudo et al.