Thermodynamics of Complexation of Amino Acids Containing Various Functional Groups with 18-Crown-6 in Water

Equilibrium constants, free energies, enthalpies, and entropies of complexation of amino acids containing various functional groups (L-isoleucine, L-histidine, DL-methionine, L-serine, L-threonine, L-asparagine, L-glutamine) with 18-crown-6 in water at 298.15 K are measured by the calorimetric method. The effect of side groups of amino acids on the stability constants of complexes is analyzed. The effect of the solvating properties of solvent on the complexation thermodynamics is demonstrated; the relationship between the enthalpies of complexation and enthalpies of hydration of amino acids is considered.