Thermodynamics Research Center / ThermoML | Journal of Chemical Thermodynamics

ABSTRACT

The standard (p 1/4 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 115H2O (aq), measured by rotating bomb combustion calorimetry. For these four compounds, the standard molar enthalpies of vaporization, Dg l H m, at T = 298.15 K, were obtained by high temperature Calvet microcalorimetry. The values obtained were: Compound DfH m olP=okJ mol 1 P Dgl H m o298:15 KP=okJ mol 1 P Methyl 2-thiophenecarboxylate (l) 301.2 +- 1.7 57.6 +- 1.2 Ethyl 2-thiophenecarboxylate (l) 327.2 +- 2.0 56.6 +- 1.3 Ethyl 2-thiopheneacetate (l) 361.8 +- 2.3 61.8 +- 1.3 Ethyl 3-thiopheneacetate (l) 358.9 +- 2.2 63.2 +- 1.3 The standard (p 1/4 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.