Absorption spectra of some pyridine and pyridine N-oxide derivatives in oleum

The absorption spectra of a number of pyridlne and pyridine N-oxide derivatives in media of different acidity functions have been investigated. The bathochromic shift of the shortwave absorption band in oleum is interpreted as a consequence of the addition of a proton to the conjugate acid. The formation of a hydrogen bond between the 3-hydroxy derivative of the heterocyclic compounds investigated and the oleum, appearing as a hypsochromic shift of the long-wave absorption band, has been detected. This phenomenon is absent in the case of the 2-methoxy derivative.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 963–966, July, 1973.