A conductance study of the interaction between ammonium ion and 18-Crown-6 (18C6), dicyclohexano18-crown-6 (DC18C6), ditertbutyl-dicyclohexano-18-crown-6 (t-bu)2DC18C6, diaza-15-crown-5 (DA15C5), dibenzo-21-crown-7 (DB21C7) and N-Phenylaza-15-crown-5 (NPA15C5) in acetonitril-dimethylsulfoxide mixture was carried out at various temperatures. The formation constants of the resultant 1:1 complexes were determined from themolar conductance-mole ratio data and found to vary in the order of DA15C5 > DC18C6 > 18C6 > (t-bu)2DC18C6 > DB21C7 > NPA15C5. The enthalpy and entropy of the complexation reactions were determined from the temperature dependence of the formation constants
