Thermodynamics of complex formation in mixed solvents K and ΔH for the formation reaction of [Gly18C6] at 298.15 K

Influence of the composition of aqueous dimethylsulfoxide solvent on thermodynamics of complexing between 18-crown-6-ether and D,L-alanine

“…Desolvation of 18C6 dominates over the des olvation of [Ala-18C6] and determines changes in the energetics of formation [Ala-18C6] and while changes in Δ tr H°(Ala) are close to 0. Such a relation of solvation contributions from reagents was observed upon the formation of 18C6 molecular complexes with glycine in Н 2 О-EtOH [3], Н 2 О-МеАс [3], and H 2 O-DMSO [6]. As in [3,6] …”

“…The Ala-18C6 stability and exothermicity of its formation increase with a rise in the dimethylsul foxide concentration in the mixed solvent; the enthalpy component of the Gibbs free energy thus dominates over the entropy component. In [3,6], we found a similar influence for the composition of water-ethanol, water-aceton, and water dimethyl sulfoxide solvents on the formation of molecular com plexes [Gly-18C6].…”

“…In studying the molecular complexes between 18C6 and aminoacids [3][4][5][6] in aqueous solutions of ethanol, dimethylsulfoxide, and acetone, it was found that the increasing stability of complexes and the growing exothermic nature of complexing is associ ated with the weakening solvation of reagents upon increasing the concentration of the nonaqueous com ponent of a mixed solvent.…”

Complexation of Cyclodextrins with Benzoic Acid in Water-Organic Solvents: A Solvation-Thermodynamic Approach

“…The changes in the stability of the molecular complexes [BA⊂β-CD] were compared with those of the molecular complexes of 18-crown-6 ether (18C6) with glycyl–glycyl–glycine (3Gly), [3Gly18C6] [ 51 , 52 ], glycine (Gly), [Gly18C6] [ 53 , 54 ] and phenylalanine (Phe) [Phe18C6] [ 55 , 56 ] during the transfer from water to water–organic solvents ( Figure 10 and Figure 11 ). These objects were selected for comparison of the “guest–host” molecular complexes formation in aqueous-organic solvents.…”

“…The changes in the enthalpy of the reactions of the formation of complexes [BA⊂β-CD], [3Gly18C6] [ 51 , 52 ], [Gly18C6] [ 53 , 54 , 55 ] and [Phe18C6] [ 56 , 57 ] when transferred from water to water–organic solvents are shown in Figure 12 and Figure 13 . In the case of water–ethanol solvent the increase of the exothermicity of the reaction is observed for all examined molecular complexes [BA⊂β-CD], [3Gly18C6], [Gly18C6] and [Phe18C6].…”