AbstractThe medium‐resolution Raman spectrum of benzoic acid vapour has been recorded. Comparison of the high‐frequency spectrum with the internal spectra of substituted and similar molecules indicates that previous assignments of the spectra should be revised. Three possible explanations are proposed for the broad feature observed at very low frequencies. Two of them lead to the conclusion that there is a very low barrier for hindered rotation around the CC bond connecting the carboxylic group with the phenyl