Thermochemical properties of two nitrothiophene derivatives

Abstract

This article reports the values of the standard (p ^o = 0.1 MPa) molar enthalpies of formation, in the gaseous phase, ${{\Updelta}}_{\text{f}} H_{\text{m}}^{\text{o}} \left( {\text{g}} \right),$ at T = 298.15 K, of 2-acetyl-5-nitrothiophene and 5-nitro-2-thiophenecarboxaldehyde as −(48.8 ± 1.6) and (4.4 ± 1.3) kJ mol⁻¹, respectively. These values were derived from experimental thermodynamic parameters, namely, the standard (p ^o = 0.1 MPa) molar enthalpies of formation, in the crystalline phase, ${{\Updelta}}_{\text{f}} H_{\text{m}}^{\text{o}} \left( {\text{cr}} \right) ,$ at T = 298.15 K, obtained from the standard molar enthalpies of combustion, ${{\Updelta}}_{\text{c}} H_{\text{m}}^{\text{o}} ,$ measured by rotating bomb combustion calorimetry, and from the standard molar enthalpies of sublimation, at T = 298.15 K, determined from the temperature–vapour pressure dependence, obtained by the Knudsen mass loss effusion method. The results are interpreted in terms of enthalpic increments and the enthalpic contribution of the nitro group in the substituted thiophene ring is compared with the same contribution in other structurally similar compounds.