The influence of steric effect on H-1 NMR, C-13 NMR, and IR spectra of methylated derivatives of 4-nitropyridine N-oxide

The H-1 NMR, C-13 NMR, and IR spectra of 2-methyl-, 3-methyl-, 2,3-dimethyl-, a,5-dimethyl-, a,6-dimethyl-, 3,5-dimethyl-, and 2,3,6-trimethyl-4-nitropyridine N-oxides were interpreted. The influence of electron properties of substituents on changes of chemical shifts was analyzed. It was found that ''ortho-effect'' of the methyl group inhibits paramagnetism of the nitro group. The ratio between a given substituted heterocyclic compound, its parent compound and the identically substituted benzene derivatives has been determined. It was found that the effect of the nitro group on chemical shift and the so-called track donation is modified by electronegativity and the position of the substituent.