Integrated intensities of O-H stretching bands: Fundamentals and overtones in vapor-phase alcohols and acids

Integrated intensities have been measured for O-H stretching vibrational bands, including fundamentals and the first three overtones for methanol, ethanol, 1-propanol, 2-propanol, tert-butyl alcohol, 2,2,2-trifluoroethanol, nitric acid, and acetic acid. Fundamental band strengths are seen to increase with the electronegativity of the adjacent substituent, though directly analogous trends for overtones are less apparent. However, substituent electronegativity does parallel the proportional decrease in overtone intensity, relative to the corresponding fundamental. In addition, the intensities have been modeled using a two-parameter, linear-exponential dipole moment function. The agreement between observed and calculated intensities is fair, but the overall shapes of the fitted dipole moment functions also parallel the inductive nature of the substituent. Some tentative rationale for the observed intensity trends is offered, but definitive claims cannot be made without further investigation. The current results are finally compared to a few studies of C-H-containing compounds, and differences in the respective intensity data are discussed.