The ratio of the Raman intensity of the trans to gauche bands and also the optical density ratio, for n-alkyl bromides, has been examined in liquid, dilute solution, and vapor (for n-propyl bromide) and the temperature dependence of the Raman intensity ratio obtained over the range −80° to +80 °C. for the liquids. Both Raman and infrared ratios become constant for the higher members of the series but are measurably different for n-butyl and n-propyl bromide. The results are consistent with a very small difference in energy between gauche and trans forms in liquid, solution, or vapor, and can be interpreted semiquantitatively by assuming appropriate trans–gauche energy differences in the carbon chain.