Vapour spectrum of benzoxazole in the near ultraviolet

The absorption spectrum of benzoxazole was investigated in the near u.v. region. Two band-systems are clearly discernible. The first system Aâ†�X is composed of about 150 bands at 36,000–40,000 cm.–1. It degrades into a continuum of low intensity and then the absorption rises in the second system Bâ†�X to reach a maximum at 44,500 cm.–1.For the Aâ†�X system, partial vibrational analysis is given based on the electronic origin at 36,491 cm.–1. Assignments are consistent with the i.r. data, and Raman lines were also measured. A strong sequence –61 cm.–1 is interpreted as n(202′– 263″) cm.–1, both frequencies being of A″ symmetry. The electronic transition appears to be localized mainly on the benzene ring. Solvent shift and intensity of the higher frequency transition are of the same order of magnitude as those observed in monosubstituted benzene derivatives such as anisole and aniline.