No abstract

The enthalpies of solution of 1-aminobutylphosphonic acid (Nval P ), 1-amino-2-methylpropylphosphonic acid (Val P ), 1-amino-3-(methylthio)propylphosphonic acid (Met P ), N-methyl-1-aminopropylphosphonic acid (Me-Hal P ), and N,N-dimethyl-1-aminopropylphosphonic acid (Me 2 -Hal P ) in water and aqueous urea solutions were measured within the molality range from (0.5 to 4) mol (U)•kg −1 (H 2 O) at a temperature of 298.15 K. The results obtained were used to determine the standard enthalpies of solution, whose values were then used to calculate the enthalpic heterogeneous pair (phosphonic amino acid−urea) interaction coefficients.

The enthalpies of solution of aminomethylphosphonic acid (GlyP), 1-aminoethylphosphonic acid (AlaP), and 1-aminopropylphosphonic acid (HalaP) have been measured in water and aqueous urea solutions at 298.15 K. From the obtained experimental results, the standard enthalpies of solution of aminophosphonic acids (AP) in water–urea solutions have been determined. These data were used to calculate the heterogeneous enthalpic pair interaction coefficients based on McMillan–Mayer's formalism. These values were interpreted in the terms of the hydrophobic effect of the side chains of aminophosphonic acids on their interactions with a molecule of urea in water.