Calorimetric titrations are used to study the interactions between the crown ether 18-crown-6 and several alpha,omega-diamino dihydrochlorides in aqueous solution. These complexes are formed by ion-dipole interactions between the positively charged nitrogen atoms and the oxygen donor atoms of the crown ether. Depending on the experimental conditions, the formation of 1:1 or 2:1 complexes (ligand:diamines) can be studied. The solvation of the ligand and the amines are responsible for the observed thermodynamic values. The number of water molecules released during the reaction were calculated from the determined reaction entropies. Formation of 1:1 complexes distorts the solvation shell around the molecules. As a result, the number of solvent molecules released during the formation of the 2:1 complexes is slightly smaller than the number released from formation of the 1:1 complex. No experimental evidence is observed for the formation of complexes between one crown ether and two protonated amino groups.