Standard molar enthalpies of formation and of sublimation of 2-thiophenecarboxamide and 2-thiopheneacetamide

The standard (p∘ = 0.1 MPa) molar enthalpies of formation of crystalline 2-thiophenecarboxamide and 2-thiopheneacetamide were calculated from the standard molar energies of combustion, in oxygen, to yield CO2(g), N2(g) and H2SO4 · 115 H2O(aq), measured by rotating-bomb combustion calorimetry, at T = 298.15 K.The vapour pressures of these two compounds were measured as functions of temperature by Knudsen-effusion mass loss technique; from the Clausius–Clapeyron equation the standard molar enthalpies of sublimation, at T = 298.15 K, were derived.The results were as follows:Compounds-ΔcUm∘(cr)-ΔfHm∘(cr)ΔcrgHm∘kJ·mol-1kJ·mol-1kJ·mol-1kJ·mol-1kJ·mol-1kJ·mol-12-Thiophenecarboxamide3108.7 ± 1.1171.1 ± 1.2107.1 ± 0.42-Thiopheneacetamide3760.7 ± 1.6197.2 ± 1.8109.2 ± 0.5Full-size tableTable optionsView in workspaceDownload as CSVFrom these values, the standard molar enthalpies of formation of both compounds in their gaseous phase were derived and interpreted in terms of enthalpic increments and molecular structure.