Study of density and viscosity of aqueous solution of alkali metal salt with 18-crown-6 at 308.15K.

Abstract

Molecular interaction of aqueous solution of alkali metal cation (Na⁺, K⁺) with 18-crown-6 investigated at 308.15K to calculate the interaction complexation behavior and binding affinity of macrocyclic 18-crown-6 ether ligand. This investigation based on the selective host-guest complexation. It was carried out by measurement of density and viscosity. The experimental data of density and viscosity were used to evaluate excess parameters such as excess molar volume (V^E), viscosity deviation (∆η) apparent molar volume (ɸ_v), by providing insight into the cation selectivity of 18-crown-6. This investigation indicated a strong interaction towards potassium ion (K⁺) with 18-crown-6, with optimal cavity size of crown ether, while smaller and larger size alkali metal cations exhibited weaker interaction. This investigation highlights the vital role of ionic size and host guest complexation in leading stability of complexes of 18-crown-6 ether. The binding sequence of aqueous solution of alkali metal cation with 18-crown-6 is - K⁺ > Na⁺

Keywords: Aqueous solution of alkali metal cations, viscosity, density, complexation, 18-crown-6, molecular interaction.