The influence of water molecules on the complex formation between K+ and 18-crown-6 and the cryptand (222) in chloroform

The complexation formation between potassium dibenzyldithiocarbamate and 18-crown-6 and the cryptand (222) was studied in chloroform using calorimetric titrations. By variation of the molar ratio of the salt and water the influence on the reaction enthalpies was studied. With increasing concentration of water in chloroform the values of the reaction enthalpies decrease for both ligands. The microsolvation of the cation or ion pair present in solution by the water molecules has a pronounced effect on the reaction. Thus the presence of very small amounts of water cannot be neglected for the extraction of cations from aqueous to chloroform solution. (C) 2001 Elsevier Science B.V. All rights reserved.