A new calorimetric titration technique for the study of 2:1 crown ether complexes in solution

Abstract

The formation of 1:1 and 2:1 complexes is treated mathematically. The influence of the values of the stability constant K 2 and reaction enthalpy Δ H 2 upon the heat produced during calorimetric titrations is calculated. From these results the experimental conditions for the simultaneous calculation of stability constants and reaction enthalpies for the formation of 1:1 and 2:1 complexes of crown ethers with cations from calorimetric titrations are discussed. The mathematical treatment of these experiments is rather difficult if four parameters have to be fitted to the experimental data. Using the information obtained from the calculations an indirect method which is easy to perform is investigated for studying the complexation reactions. Even in this case no four-parameter fit is successful. Using the values for the 1:1 complex formation obtained directly it is possible to calculate the values for the 2:1 complex formation without any problems. This is demonstrated for three different reactions.