Experimental and Theoretical Thermochemical Study of Nitrobenzaldehyde Isomers

Using different calorimetric techniques, the thermophysical and thermochemical properties of 2-, 3-, and 4-nitrobenzaldehyde were determined, including combustion energies, sublimation enthalpies, heat capacities, vaporization enthalpies, and enthalpies of formation in the gas phase. The latter were also calculated by means of the Gaussian G4 composite method and atomization reactions. Equations of heat capacity as functions of temperature, in the condensed phase, were measured experimentally, whereas the equations for heat capacities in the gas phase were calculated via computational techniques. By means of an isoperibolic combustion calorimeter, combustion energies were also determined. Sublimation enthalpies were obtained through thermogravimetry, by measuring the rate of mass loss as a function of temperature and applying the Langmuir equation. Fusion temperatures, fusion enthalpies, and heat capacities were determined using differential scanning calorimetry. The energetic influence of the nitro group on the aromatic ring is discussed briefly, and the presence of hydrogen bonding in 2-nitrobenzaldehyde is theoretically supported.