Knowledge Bank

Infrared and Raman spectra of the vapors of trifluoroacetic acid, acetic acid and formic acid have been observed in the regions of 3800 to $400cm-1$ and 3800 to $75cm-1$ respectively. The observation of the vapor phase Raman spectra allows a more complete vibrational analysis of these species. Identification of the monomer and dimer bands have been facilitated by two methods, both of which are based upon the temperature dependence of hydrogen bond formation. The variation of intensity with temperature allowed the identification of the monomer and dimer Raman spectra. Absorbance subtraction of a scaled monomer spectrum from combined monomer-dimer spectra allowed a mathematical separation of the monomer and dimer infrared spectra. The advantages afforded by computer handling of spectroscopic data for hydrogen bonded systems are discussed.