The association constant of macrocyclic ether-cation interactions in 1,4-dioxane/water mixtures. III - Effect of temperature on the binding

Abstract

The association constant, K-a, of Na+ with [12] crown-4, [15]crown-5 and [18]crown-6 crown ethers were determined in a binary mixture, 1,4-dioxane/water (50/50) using a Na+ ion selective electrode at different temperatures. K-a, values were determined with the relationship, 1/K-a [L-o](n+m-1) = (1-nP')(n) (1-mp')m/p', for various stoichiometries, (n:m), where P' is the mole fraction of the complexed cation. The exothermic association constants and the thermodynamic data for cation-macrocycle complexes explained in terms of Eigen-Winkler binding mechanism are given. The binding power found for Na+, however, was the highest with [18] crown-6.