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.