THERMODYNAMIC STUDY OF SOLVENT-EXTRACTION OF MONOVALENT METAL PICRATES WITH BENZO-18-CROWN-6 INTO CHLOROFORM

Thermodynamic parameters (DELTAH(ex)0 and DELTAS(ex)0) for the overall extractions of monovalent metal (Na, K, Rb, and Tl) picrates with ben zo-18-crown-6 (B18C6), and those (DELTAH(D,L)0 and DELTAS(D,L)0 for th e distribution of B18C6 were determined between chloroform and water. All the extracted B18C6 complexes were 1:1:1 complexes (B18C6:metal io n: picrate anion). The DELTAH(ex)0 and DELTAS(ex)0 values for all the metals are negative. Every extraction of the metal picrate with B18C6 is completely enthalpy driven. The DELTAH(D,L)0 and DELTAS(D,L)0 value s of B18C6 are both positive, and the partition of B18C6 is entirely e ntropy driven. Enthalpy (DELTAH(ex,ip)0) and entropy changes (DELTAS(e x,ip)0) for ion-pair extractions of B18C6-metal ion complexes with pic rate anions were calculated. All the DELTAH(ex,ip)0 and DELTAS(ex,ip)0 values are negative, and the ion-pair extractions are completely enth alpy driven.