ABSTRACT
The thermodynamic study of cation binding by crown ethers started immediately the first synthesis of crown ether in order to elucidate the nature of the cation-binding behavior in terms of the enthalpy and entropy change. The thermodynamic parameters reported are very useful in rationalizing the individual complexation reactions. In order to test the general validity of the enthalpy-entropy compensation effect in the electrostatically interacting cases, the TΔS values are plotted against the ΔH value for each type of ligand. The origin of the compensation effect is not entirely clear, nor is it attributable to a single cause since the thermodynamic parameters are affected by several perturbations. However, sometimes the enthalpy-entropy compensation is not unrealistic. According to the Lewis concept, all cation-ligand interactions are acid-base reactions. In this sense, it is interesting to survey the possibility as to whether or not the enthalpy-entropy compensation effect holds in the Brosted acid-base reaction between proton and oxygen or nitrogen ligands.
