Thermometric titration of some amines in water—acetone mixtures

The enthalpies of protonation of some N-bases in H₂O—acetone, 0, 0.25, 0.5, 0.75 and 0.95 mole fraction at 298 K have been determined by calorimetry. Solutions of amines in each solvent system were titrated enthalpimetrically with HClO₄ solution. The bases studied were piperidine, n-butylamine, 2-amino-2-methyl-1,3-propanediol, (AMP), tris(hydroxymethyl) aminomethane, tris, 2,2-bis-(hydroxymethyl-2,2′,2″-nitrilotriethanol, (bis-tris) and pyridine.The results are discussed in terms of the preferential solvation of ions by two types of solvent molecules. The enthalpy of protonation of all the bases passes through a minimum at a solvent composition of 0.75 mole fraction of acetone.