A conductance study of the association of alkali cations with 1,13-dibenzo-24-crown-8 in acetonitrile

A conductance study concerning the association of Na⁺, K⁺, Rb⁺, and Cs⁺ with 1,13-dibenzo-24-crown-8 in acetonitrile has been carried out at 35, 30, 25, 20, and 15°C. The observed molar conductivities were found to decrease significantly for mole ratios less than unity. A model involving 11 stoichiometry has been used to analyze the conductivity data. The stability constant, K, and the molar conductivity _C for each 11 complex were determined from the conductivity data by using a nonlinear least squares curve fitting procedure. The binding sequence, based on the value of log K at 25°C, is found to be Rb⁺>Cs⁺>K⁺>Na⁺. Values of H^o and S^o are reported and their significance is discussed.