Experimental study on the thermochemistry of 2,5-dimethylthiophene and its acetyl derivative

Abstract

This paper reports the values of the standard ( p ∘ = 0.1 MPa) molar enthalpies of formation, in the gaseous phase, Δ f H m ∘ ( g ) , at T = 298.15 K, of 2,5-dimethylthiophene and 3-acetyl-2,5-dimethylthiophene as (50.6 ± 1.9) kJ · mol −1 and −(123.2 ± 2.7) kJ · mol −1, respectively. These values were derived from experimental thermodynamic parameters, namely, the standard molar enthalpies of formation, in the liquid phase, Δ f H m ∘ ( l ) , at T = 298.15 K, obtained from the standard molar enthalpies of combustion, Δ c H m ∘ , measured by rotating bomb combustion calorimetry, and from the standard molar enthalpies of vaporization, Δ l g H m ∘ , at T = 298.15 K, measured by high temperature Calvet microcalorimetry. The results are interpreted in terms of enthalpic increments, molecular structure and compared with structurally similar compounds.