Effect of Solvation on the Complexation of 18-Crown-6 with Amino Acids in Aqueous-Organic Media

摘要

Our own and published data on the effect of mixed solvents on the thermodynamic parameters of molecular complexation of 18-crown-6 with glycine, D,L-alanine, and L-phenylalanine in aqueous ethanol, dimethyl sulfoxide, and acetone have been generalized. In all cases, decrease of the water fraction in mixed solvents increases the exothermic effect of complex formation. The change in the reaction enthalpy is determined mainly by variation of the enthalpies of solvation of the molecular complex and 18-crown-6, whereas the contribution of solvation of the amino acid is insignificant.