Thermochemical Studies on Thioacetamide and Tetramethylthiourea. Estimation of Stabilization Energies Due to Interaction between Thiocarbonyl Group and Neighbouring Nitrogen Atom

Standard energy of combustion at 298.15 K and standard enthalpy of sublimation as a function of temperature were determined for thioacetamide and tetramethylthiourea by oxygen bomb combustion calorimetry and sublimation calorimetry. Derived standard enthalpies of formation in crystalline and gaseous states at 298.15 K are −(70.6±1.1) and (12.7±1.2) kJ mol−1, respectively, for thioacetamide, and −(38.3±2.3) and (44.7±2.4) kJ mol−1, respectively, for tetramethylthiourea. Stabilization energies of these molecules were evaluated by estimating the standard enthalpies of formation in gaseous state for the hypothetical reference structures by use of the group contribution method.