Experimental study on the thermochemistry of 3-nitrobenzophenone, 4-nitrobenzophenone and 3,3′-dinitrobenzophenone

Abstract

The standard ( p° = 0.1 MPa) molar enthalpies of combustion, Δ c H m ∘ , for the 3- and 4-nitrobenzophenones and for the 3,3′-dinitrobenzophenone, in the crystalline state, were determined, at the temperature T = 298.15 K, using a static bomb combustion calorimeter. For these compounds, the standard molar enthalpies of sublimation, Δ cr g H m ∘ , at T = 298.15 K, were determined by Calvet microcalorimetry. For the 3- and 4-nitrobenzophenones the vapour pressures as function of temperature were measured by the Knudsen effusion technique and the standard molar enthalpies of sublimation, Δ cr g H m ∘ , at T = 298.15 K, were derived by the Clausius–Clapeyron equation. The results are as follows: - Δ c H m ∘ ( cr ) / ( kJ · mol - 1 ) Δ cr g H m ∘ / ( kJ · mol - 1 ) Calvet Knudsen 3-Nitrobenzophenone 6324.5 ± 1.4 123.3 ± 2.4 121.6 ± 0.6 4-Nitrobenzophenone 6327.8 ± 1.9 122.3 ± 2.7 122.9 ± 0.7 3,3′-Dinitrobenzophenone 6154.6 ± 2.2 147.4 ± 3.9 These values were used to derive the standard molar enthalpies of formation of the compounds in their condensed and gaseous phases, respectively. For 3- and 4-nitrobenzophenones, the standard ( p° = 0.1 MPa) molar enthalpies, entropies and Gibbs functions of sublimation, at T = 298.15 K, were derived. The derived standard molar enthalpies of formation in the gaseous state are analysed in terms of structural enthalpic increments.