Interaction-related volumetric and some other properties of urea solutions in aqueous N-tetramethylglycoluril (the mebicar drug) at different temperatures and under the ambient pressure

Abstract Densities for solutions of urea in aqueous mebicar (N-tetramethyl-substituted glycoluril) were measured using a hermetically sealed vibrating-tube densimeter, with an uncertainty of ~3.0 × 10−2 kg∙m−3, at T = (278.15, 288.15, 298.15, 308.15, and 318.15) K and p = (99.6 ± 0.8) kPa. The solution molality was ranged from (0.026 to 0.101) mol·kg−1 for the aqueous mebicar and from ca. (0.1 to 0.4) mol·kg−1 for the solute urea. The density data were used to calculate the apparent molar volumes and expansibilities (down to infinite dilution) for urea as a solute, as well as urea – urea and urea – mebicar pairwise interaction coefficients over the whole temperature range being chosen. The calorimetrically derived effects of urea dissolution in the aqueous mebicar at T = 298.15 K were also included in discussing. The results were compared with the previously obtained those for the similar ternary system (water + mebicar + glycine). It was concluded that the hydrophilic constituent (via H-bonding) are predominant in the solute – co-solute interaction effects and the mebicar has an overall stabilizing influence on the process of urea hydration.