Thermochemical study of the isomeric compounds: 3-acetylbenzonitrile and benzoylacetonitrile

Abstract The standard ( p ° = 0.1 MPa) molar enthalpies of formation of 3-acetylbenzonitrile and benzoylacetonitrile, in the crystalline phase, were derived from the respective standard massic energies of combustion measured by static bomb combustion calorimetry, in oxygen, at T  = 298.15 K. The standard molar enthalpies of sublimation, at T  = 298.15 K, were measured by Calvet microcalorimetry. From the above experimentally determined enthalpic parameters, the standard molar enthalpies of formation in the gaseous phase, at T  = 298.15 K, are found to be: (52.4 ± 2.1) kJ · mol −1 and (74.8 ± 2.5) kJ · mol −1 for 3-acetylbenzonitrile and benzoylacetonitrile, respectively. Molecular structures were computed using highly accurate ab initio techniques. Standard molar enthalpies of formation of the experimentally studied compounds were derived using an appropriate set of working reactions. Very good agreement between the calculated and the experimental values was obtained, so the calculations were extended to the estimates of the standard molar enthalpies of formation of 2- and 4-acetylbenzonitriles whose study was not performed experimentally. Our results were further interpreted and rationalized in terms of the enthalpic stability and compared to other relevant disubstituted benzenes.