Thermodynamics Research Center / ThermoML | Journal of Chemical and Engineering Data

ABSTRACT

Molar enthalpies of solution in water, ?solHm, of thiourea, methylthiourea, ethylthiourea, dimethyl-1,3-thiourea, diethyl-1,3-thiourea, and tetramethyl-1,1,3,3-thiourea were measured at T = (296.84, 302.45, and 306.89) K by isothermal calorimetry. Experimental results were used to derive molar enthalpies of solvation at infinite dilution (i.d.), ?solvHm8, changes in heat capacity due to the solution process, ?solCp,m8, and partial molar heat capacities at i.d., Cp,28, at T = 298.15 K. The methylene group contributions to the enthalpy of solvation and partial molar heat capacity were -4.5 kJ*mol 1 and 88.5 J*K 1*mol 1, respectively, in good agreement with our earlier data for N-alkylureas and the literature data for various homologous series of alkyl-substituted compounds. The contributions of the functional groups to both ?solvHm8 and Cp,28 were derived by employing additive schemes and compared with our earlier data for urea and corresponding N-alkylureas. Hydration behavior at the i.d. of thiourea, urea, and corresponding N-alkyl derivatives were compared and discussed.