A "Universal" Spectroscopic Map for the OH Stretching Mode in Alcohols

Empirical maps are presented for the OH stretching vibrations in neat alcohols in which the relevant spectroscopic quantities are expressed in terms of the electric field exerted on the hydrogen atom by the surrounding liquid. It is found, by examination of the four lowest linear alcohols, methanol, ethanol, n-propanol, and n-butanol, that a single map can be used for alcohols with different alkyl groups. This "universal" map is in very good agreement with maps optimized for the individual alcohols but differs from those previously developed for water. This suggests that one map can be used for all alcohols, perhaps even those not examined in the present study. The universal map gives IR lineshapes in good agreement with measured spectra for isotopically dilute methanol and ethanol, while the two-dimensional IR photon echo spectra give results that differ from experiments. The role of non-Condon effects, reorientation dynamics, hydrogen bonding, and spectral diffusion is discussed.