Energetics of thiophenecarboxaldehydes and some of its alkyl derivatives

The standard (p∘ = 0.1 MPa) molar enthalpies of combustion, ΔcHm∘, for the liquids 2-thiophenecarboxaldehyde, 3-thiophenecarboxaldehyde, 3-methyl-2-thiophenecarboxaldehyde, 5-methyl-2-thiophenecarboxaldehyde, and 5-ethyl-2-thiophenecarboxaldehyde were determined, at the temperature of 298.15 K, using a rotating-bomb combustion calorimeter. For these five compounds, the standard molar enthalpies of vaporization, ΔlgHm∘, at T = 298.15 K were obtained by high temperature Calvet microcalorimetry. Compounds-ΔcHm∘(l)/(kJ · mol−1)-ΔfHm∘(l)/(kJ · mol−1)ΔlgHm∘(298.15K)/(kJ · mol−1)2-Thiophenecarboxaldehyde3079.2 ± 1.462.0 ± 1.554.9 ± 1.13-Thiophenecarboxaldehyde3081.2 ± 1.460.0 ± 1.552.6 ± 1.23-Methyl-2-thiophenecarboxaldehyde3722.2 ± 1.598.3 ± 1.757.7 ± 1.35-Methyl-2-thiophenecarboxaldehyde3727.0 ± 1.593.5 ± 1.756.2 ± 1.25-Ethyl-2-thiophenecarboxaldehyde4367.6 ± 1.8132.3 ± 2.062.2 ± 1.3Full-size tableTable optionsView in workspaceDownload as CSVThe standard molar enthalpies of formation of the title compounds, in the gaseous phase, were derived through these experimental thermodynamic parameters and the results are interpreted in terms of structural effects and compared with structurally similar compounds.