Advances in quantum chemistry in the 1990's have resulted in improvements in the modeling of molecules and in
calculating energies, transition structures, and modes of vibration, resulting in the capability to approximate vapor-phase
infrared spectral signatures of chemicals using ab-inito calculations. These approaches provide a means of deriving
signatures of vapor-phase chemicals, or gases, whose spectra may be too difficult to measure through traditional means.
The purpose of this paper will be to review the limitations and accuracies in the modeling of spectral signatures using
different methods and basis sets. Comparisons will be made between calculated signatures and laboratory measured