Effect of solvent molecular structure on vibration—rotation spectra of DCl and CO solutes in cycloalkanes

Infrared vibration—rotation spectra have been obtained for DCl and CO in a variety of cyclic and bicyclic alkanes and in alkyl-substituted cyclopentanes and cyclohexanes. The band shapes for CO depend on solvent free volume. For DCl they are sensitive to solvent structure, the rotation being perturbed by surface features (“roughness”) of the surrounding molecules. Molecular roughness is assessed qualitatively either through inspection of molecular models or through _V*, the solvent volume at close-packing, obtained from equation of state data.