CHIRAL RECOGNITION IN AQUEOUS-SOLUTIONS AT 25-DEGREES-C - A CALORIMETRIC STUDY OF THE INTERACTION BETWEEN ENANTIOMERIC ALPHA-AMINO-ACIDS OF DIFFERENT ALKYL CHAIN-LENGTH

Cross-homo- and cross-heterotactic enthalpic coefficients, h(x)D(y)D or h(x)L(y)L and h(x)D(y)L respectively, were determined at 25-degrees-C, measuring the enthalpies of dilution of ternary aqueous solutions containing two different alpha-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.