Enthalpic interactions of N,N-dimethylformamide in aqueous glucose and sucrose solutions at 298.15 K

Enthalpies of dilution of N,N-dimethylformamide (DMF) in aqueous sucrose and glucose solutions have been determined using an isothermal calorimeter (4400 IMC) at 298.15 K. The values of dilution enthalpy were used to determine homogeneous enthalpic interaction coefficients which characterize the interactions of examined DMF in aqueous sugar solutions. The results show that enthalpic pair interaction coefficients h2 of DMF are all positive in aqueous sugar solutions and pass through a maximum, respectively, at m ≈ 0.5 mol kg−1 of sucrose and at m ≈ 0.55 mol kg−1 of glucose in mixed solvents. In the meantime the h2 coefficients of DMF in aqueous sucrose solutions are more positive than that in aqueous glucose solutions. The variations of the enthalpic pairwise interaction coefficients with the mass fraction of sugar in mixtures are interpreted in terms of solute–solute and solute–solvent interactions.