Enthalpies of transfer of urea and methyl-substituted ureas from water to methanol at 298.15 K

The enthalpies of solution of urea and its N-methyl-substituted analogues (methylurea, 1,1-dimethylurea, 1,3-dimethylurea, and 1,1,3,3-tetramethylurea) in water and methanol were measured at 298.15 K. Enthalpies of transfer from water to methanol were calculated. The enthalpies of transfer of methyl-substituted ureas are endothermic, the enthalpy of transfer of urea is negative. It has been concluded that the structure-making effects do not play the key role in methanol. The earlier assumption of an independent solvation of either side (alkylated or unsubstituted amino group) of the molecules is supported.