OPTICAL-CONSTANTS OF ALCOHOLS IN THE INFRARED

We have measured the spectral reflectance R(v) at near-normal incidence for methanol, ethanol, 1-propanol, 1-butanol, and 1-pentanol in the spectral range 6700-350 cm-1. From the measured spectral reflectance, we have used Kramers-Kronig phase-shift analysis to obtain the real n(v) and imaginary k(v) parts of the complex index of refraction of these liquids in the range 4000-400 cm-1. Our results indicate that the strength S = ∫k(v) dv for the OH-stretch bands in all these alcohols is directly proportional to the number of OH groups per unit volume; similar relations have been established for CH- and CO-stretch bands. Our results make it possible to state absorption cross sections for stretch vibrations of OH, CH, and OC groups; the CH stretch cross section for absorption in alcohols is very nearly the same as the CH-stretch cross section previously established for absorption in liquid alkanes. We suggest that characteristic group intensities can play an important role in intensity spectroscopy similar to the role that characteristic group frequencies have played in frequency spectroscopy. © 1979 American Chemical Society.