Rotational isomerism. XI. Raman spectra of n-butane, 2-methylbutane, and 2, 3-dimethylbutane

Raman spectra have been obtained for n-butane, 2-methylbutane, and 2, 3-dimethylbutane in the vapor and solid (−196°C) phases. The low temperature spectra of the solids undergo a marked simplification due to the disappearance of all but one of the rotational isomers. This enabled band pairs in the vapor spectrum to be identified with the appropriate rotational isomers. From the temperature dependence of selected band pairs the enthalpy difference between the rotational isomers was obtained for each compound in the vapor phase.