Matrix isolation FT-IR and theoretical DFT/B3LYP spectrum of 1-naphthol.

Abstract The FT-IR spectrum of 1-Naphthol isolated in an argon matrix is performed and compared to the infrared spectra calculated at the DFT (B3LYP)/6-31+G(d) level for cis -1-Naphthol and trans -1-Naphthol rotamers in order to clarify the existence of both rotamers in the standard temperature. Comparison of the computed and the experimental matrix spectra reveals the presence in 1-Naphthol argon matrices in the standard temperature of both cis and trans rotameric forms of 1-Naphthol, the last predominating. The relative stability of the trans -1-Naphthol rotamer has also been supported by a fit comparison between the difference of predicted total energy ( E TC ) of both rotamers of 0.00195 a.u. corresponding to 5.12 kJ mol −1 and the variation of the standard free Gibbs energy of rotamerization ( Δ G r ° ) of 5.06 kJ mol −1 . Almost all 51 active vibrational modes of 1-Naphthol have been assigned. The stretching vibration of the OH group ( ν OH ) appears to be the unique vibrational mode distinguishing the cis -1-NpOH rotamer from the trans -1-NpOH rotamer in FT-IR spectrum.