The role of preferential interactions between similar domains in determining the behavior of aqueous solutions of aminoalkanols. A microcalorimetric study

Enthalpies of dilution of binary aqueous solutions containing 1 mol kg-1 NaOH as cosolvent and the homologous series of α,ω-aminoalkanols and 2-amino-1-alkanols as solutes have been determined by flow microcalorimetry at 298 K. Enthalpic self and cross interaction coefficients of the virial expansion of the excess enthalpies were evaluated. These coefficients are positive and increase at increasing alkyl chain length. The difference between the coefficients of positional isomers of aminoalkanols resembles that shown by the corresponding diols in water. The cross interaction coefficient relative to the ternary system containing hexane-1,6-diamine and hexane-1,6-diol is smaller than those relative to the respective binary solutions. The coefficients were interpreted using the "preferential configuration" model: it is inferred that interactions between like hydrophilic groups are preferred when compared to the like-unlike ones.