Knowledge Bank

The Raman $(4000to50cm-1)$ and far infrared $(370to50cm-1)$ spectra of gaseous 1,1,1,3,3,3-hexafluoro-2-propanol $((CF3)2CHOH)$, 1,1,1-trifluoro-2-ethanol $(CF3CH2OH)$, as well as the O-D compounds, have been recorded. Particular attention has been given to the O-H stretch and low frequency spectral regions, where evidence is found for the existence of both the trans and gauche conformers for all of these molecules. From simulations of observed gas phase infrared band profiles, it was possible to assign the OH stretching modes to the gauche and trans conformers. From relative intensities of the corresponding Raman lines as a function of temperature, the enthalpy difference in the gas phase has been determined for each molecule. Fundamental O-H torsions have been observed for all of the conformers for all of these alcohols. From these observed data, the asymmetric potential function for the internal rotation has been determined for each molecule. Additionally, the respective $CF3$ or $CH3$ torsional modes have been observed from which internal rotational barriers have been calculated.