Abstract: A chemical interaction model has been established for the hydrophobic self- association of aliphatic α- amino acids in aqueous solutions. In order to obtain the parameters of the model equation, dilution enthalpies of 5 aliphatic α- amino acids aqueous solutions have been measured at 298.15 K by flow microcalorimetry. The equilibrium constants (K), enthalpy change (ΔHm) and entropy change (ΔSm) have been determined for the equal- step association. It was found that between enthalpy and entropy exists a good compensation relationship. In addition, partial molar excess entropies of water in solutions (SE1) were calculated, and were discussed according to the hydration model for aliphatic α- amino acids. Noteworthily, the parameters in the model equation can be used to explain the homogeneous enthalpic interaction coefficients in McMillan- Mayer model to some extent.

Key words: α-amino acids, Hydrophobic self-association, Chemical model, Dilution enthalpy, Flow microcalorimetry