Chiral recognition in aqueous solutions at 25 °C. A calorimetric study of the interaction between enantiomeric α-amino acids of different alkyl chain length

Cross-homo- and cross-heterotactic enthalpic coefficients, [Formula: see text] respectively, were determined at 25 °C, measuring the enthalpies of dilution of ternary aqueous solutions containing two different α-amino acids of the same or different chirality. Differences of about 200–300 J mol−2 kg between cross-homo- and cross-heterotactic coefficients were found, well beyond the experimental uncertainty. The role of the zwitterionic interaction, already proposed to explain the nature of chiral recognition, was strengthened. Key words: α-amino acids, excess enthalpy, chiral recognition.