Enthalpies of transfer of Mebicarum from water to aqueous solutions of carbamide and its methyl-substituted derivatives at 298.15 K

The standard molar enthalpies of solution of Mebicarum (MbCA) in aqueous solutions of carbamide (CA), 1,3-dimethylcarbamide (1,3-DMCA), and 1,1,3,3-tetramethylcarbamide (TMCA) of various molalities, as well as the enthalpies of dilution of solutions of these compounds, were measured at 298.15 K. The enthalpy of transfer of MbCA from water to aqueous solutions of 1,3-DMCA exhibits an unusual dependence on the concentration of 1,3-DMCA. An analysis of the McMillan-Mayer enthalpy parameters of pair interactions revealed that the hydration of MbCA should be regarded as a superposition of the hydrophobic and hydrophilic mechanisms, with the latter one being predominant.