摘要：Infrared absorption spectra of pyridine 1-oxide and 15 kinds of its alkyl derivatives were measured and characteristic absorption band for the N-oxide group was established. The effect of ring substituents on the N-O frequency and the effect of the introduction of N-O function on ring vibration were discussed in comparison with the spectra of corresponding pyridine bases. The absorption of strong intensity always appearing in the region between 1200 and 1300 cm-1 in these compounds were assigned to that based on the N-O stretching mode. This absorption was always displaced to lower frequencies in the presence of methanol, thereby proving its solvation effect. The frequencies of this absorption showed sensitive relationship to the position of the alkyl group in the ring, the effect being especially marked in 3-alkyl group which caused a shift to the higher frequency. A reasonable relation was found to exist between N-O frequency and electronical nature of the substituents in several of the 4-substituted pyridine 1-oxides. There was no marked relationship between the out-of-plane bending frequencies of ring hydrogen in 1-oxides and those in corresponding pyridines. The behavior of the ring double-bond vibration in 1-oxide compounds was contrasting to that of the corresponding pyridines.
