The standard (p degrees = 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 Delta H-f(m)degrees(g) = -(99.4 +/- 1.6) kJ.mol(-1) and Delta H-f(m)degrees(g) = -(99.1 +/- 1.7) kJ.mol(-1), respectively, and these derived values are analyzed in terms of structural enthalpic increments. (c) 2011 Elsevier Ltd. All rights reserved.