Abstract: Thermodynamic functions of the coordination reactions of newly synthesized 2,3-benzo-8,15-dimethyl-18-crown-6 with several alkali and alkaline earth chlorides in aqueous solution were studied by calorimetric titration. The results show that only barium-ion coordinated with the crown, while the other alkaline earth and alkali metal ions did not coordinate to any detectable degree because they do not have enough activity toward the crown due to its limited solubility in solution (0.005M) and very small enthalpy of reaction.