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

Abstract

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 Δ f H m ∘ (g) = - ( 99.4 ± 1.6 ) kJ · mol - 1 and Δ f H m ∘ (g) = - ( 99.1 ± 1.7 ) kJ · mol - 1 , respectively, and these derived values are analyzed in terms of structural enthalpic increments.