Complex formation of crown ethers and cryptands with Ba2+ in the biphasic system chloroform/water studied by titration calorimetry

Calorimetric titrations have been performed in the liquid biphasic system chloroform/water. The reactions between salts in aqueous in different crown ethers and a cryptand in chloroform solution have been studied. After saturation of each solvent with the other no heats of mixing are detected. The values of the stability constants are related to different individual reaction steps during the complex formation. The experimental values show that the complex formation itself is not measured. Other steps e.g. transfer of the salt from one solvent to the other are responsible for the calculated values. On the other hand the overall reaction enthalpies show a significant contribution resulting from the interactions between the ligands and the cation or salt. A more detailed discussion is not possible at the moment. (C) 2003 Elsevier B.V. All rights reserved.