Conductance study and thermodynamics of some substituted ammonium salts with crown ethers in aqueous solution

A conductance study of the interaction between substituted ammonium ions wi th three crown ethers in aqueous solution has been carried out at different temperatures. The formation constants of the 1 : 1 complexes at various te mperatures were determined from the molar conductance-mole ratio data and f ound to vary in the order 18C6 > 15C5 > 12C4 for the same salt and with the same crown, the formation constants vary in the order (C2H5)(3)NHCl > (C2H 5)(4)NBr > (CH3)(3)NPhI. The enthalpy and entropy of complexation were determined from the temperatu re dependence of the formation constants. The results indicate that the com plexation process is enthalpy unfavored and entropy favored. The influence on the thermodynamic data for different parameters such as cavity size of c rown ethers and nature of salt are discussed.