Thermodynamics of the protonation of some cryptands in water and methanol

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Abstract

We report the results of thermochemical studies in water and anhydrous methanol of some cryptands, L = [2.2.2], [2.2.1], of general formula represented below:

Protonation constants K1 and K2, relative to the following equilibria:
have been determined by pH-metry at 25°C, with I = 0.1 or 5 × 1010−2 M(Et4NClO4). The values of ΔH1 and ΔH2 have been determined from calorimetric measurements in both solvents. Corresponding ΔG and ΔS values have been calculated.

Results are discussed in terms of conformational changes of the mon- and biprotonated cryptands in the different solvent water and methanol.

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