Formation Constants of Dibenzo-18-crown-6 Complexes with Alkali Metal Ions in DMSO, DMF, and PC at 25°C

Abstract

Abstract The formation constants (Kf) for the 1 : 1 complexes of dibenzo-18-crown-6 (DBG) with alkali metal ions in DMSO (dimethyl sulfoxide), DMF (N,N-dimethyl formamide), and PC (propylene carbonate) have been determined conductometrically. The formation constant sequences of the alkali metal ions with DBG in DMSO, DMF, and PC are K+>Rb+>Cs+≅Na+>>Li+, K+>Rb+>Cs+>Na+>Li+, and K+>>Na+>Rb+>Cs+>Li+ respectively. The Kf value series about the same alkali metal ion among these nonaqueous solvents are given in the order of DMSO<DMF<PC. These results show that the selectivity of DBC toward the alkali metal ions is dependent on the ionic diameter and the ring-hole size of DBC, and that the donor number of the organic solvent as a component factor is important in determining the process of the formation of the DBC complexes constant.