Calorimetric study of methyl and ethyl 2-thiophenecarboxylates and ethyl 2- and 3-thiopheneacetates

The standard (p degrees = 0.1 MPa) molar enthalpies of formation, in the condensed phase, of the liquids methyl 2-thiophenecarboxylate, ethyl 2-thiophenecarboxylate, ethyl 2-thiopheneacetate, and ethyl 3-thiopheneacetate, at T = 298.15 K, were derived from the standard massic energies of combustion, in oxygen, to yield CO2 (g) and H2SO4 . 115H(2)O (aq), measured by rotating bomb combustion calorimetry. For these four compounds, the standard molar enthalpies of vaporization, Delta H-g(l)degrees(m), at T = 298.15 K, were obtained by high temperature Calvet microcalorimetry. The values obtained were: [GRAPHICS] The standard (p degrees = 0.1 MPa) molar enthalpies of formation, in the gaseous phase, were derived from the experimental results and they are interpreted in terms of enthalpic increments of the introduction of a methylene group to the substituent chain. Moreover, the results are compared with the analogue benzene derivative. (C) 2009 Elsevier Ltd. All rights reserved.