Solvent induced frequency shifts of the C—H stretching bands of n-octane. A Fourier transform infrared study

Using a Fourier transform spectrometer the frequencies and bandwidths of the infrared active C—H stretching modes of n-octane were determined in a variety of solvents with refractive indices from 1.63 (carbon disulfide) to 1.28 (n-perfluorooctane), and dielectric constants from 37.5 (acetonitrile) to 1.8 (n-perfluorooctane). The frequency shifts were correlated with the refractive indices and dielectric constants of the solvents, and fitted with the equation of David and Hallam (Spectrochim. Acta, Part A, 23, 593 (1967)). Generally, solution results in shifts to frequencies lower than those observed in the gas phase. However, solution in n-perfluorooctane resulted in a shift to a higher frequency, behavior in accord with the above equation but not previously observed.