Standard molar enthalpies of formation of 3′- and 4′-nitroacetophenones

The standard (p° = 0.1 MPa) molar enthalpies of formation, in the condensed phase, of 3′- and 4′-nitroacetophenones, presented in this work, were obtained from measurements of their combustion energies, at T = 298.15 K, using a static bomb calorimeter.The vapor pressures of the two crystalline 3′- and 4′-nitroacetophenones were measured as a function of temperature by the Knudsen effusion mass loss technique. The standard molar enthalpies of sublimation, at T = 298.15 K, were derived from the Clausius–Clapeyron equation. The standard molar enthalpies, entropies, and Gibbs functions of sublimation, at T = 298.15 K, were calculated for the two compounds.The experimental values obtained were used to calculate the standard molar enthalpies of formation of 3′- and 4′-nitroacetophenones, in the gaseous phase, as ΔfHm∘(g)=-(99.4±1.6)kJ·mol-1 and ΔfHm∘(g)=-(99.1±1.7)kJ·mol-1, respectively, and these derived values are analyzed in terms of structural enthalpic increments.

Research highlights
► The standard molar enthalpies of formation, in the condensed phase, of 3′- and 4′-nitroacetophenones have been determined by combustion calorimetry.
► The vapor pressures of the crystalline 3′- and 4′-nitroacetophenones were measured as function of temperature by the Knudsen effusion mass loss technique.
► The standard molar enthalpies, entropies and Gibbs functions of sublimation, at T = 298.15 K, were calculated for both compounds.