The Solvent Extraction of Bivalent Metal Picrates by 15-Crown-5, 18-Crown-6, and Dibenzo-18-crown-6

Abstract
The overall extraction equilibrium constants (Kex) for the 1:1:2 complexes of 15-crown-5 (15C5), 18-crown-6 (18C6), and dibenzo-18-crown-6 (DB18C6) with several bivalent metal picrates between benzene and water have been determined at 25 °C. The Kex sequences of the bivalent metal ions with 15C5, 18C6, and DB18C6 are Pb2+>Sr2+>Ba2+>Ca2+, Pb2+>>Ba2+=Sr2+>Hg2+>Ca2+, and Pb2+>Hg2+>Sr2+>Ca2+ respectively. To clarify the role of the crown ether in the extraction process, the three constituent equilibria have been investigated: the stability and the extractability of the bivalent metal ion-crown ether complex, and the distribution coefficient of the crown ether. The extractability of the bivalent metal ion-crown ether complex about the same bivalent metal ion increases with increasing size of the crown ether, and appears to be dependent on the chemical nature of the bivalent metal ion trapped in the cavity of the crown ether.

This publication has 10 references indexed in Scilit: