Molecular complex formation between L-phenylalanine and 18-crown-6 in H2O-DMSO solvents studied by titration calorimetry at T=298.15 K

The standard thermodynamic parameters (Delta(r) GA degrees, Delta(r) HA degrees, T Delta(r) SA degrees) of the reaction of molecular complex formation between 18-crown-6 ether (18C6) and l-phenylalanine (Phe), [Phe18C6], have been obtained from calorimetric titration experiments carried out by means of the microcalorimetric system TAM III (TA Instruments, USA) at T = 298.15 K in water-dimethylsulfoxide (H2O-DMSO) solvents. Results show that the increase of the DMSO concentration in the mixed solvents brings about an increase of the [Phe18C6] complex stability and of the exothermicity of the reaction of complex formation.