AbstractThe1H and13C NMR spectra of 3‐nitro‐, 5‐nitro‐ and 3,5‐dinitro‐2‐methoxypyridines have been determined. The results show the preferredcisconformation for the 2‐methoxy group, and the importance of steric repulsion between the oxygen atom of this group and those of theo‐nitro group which hinders conjugation in the 3‐nitro‐substituted derivatives. Similar steric inhibition of resonance is observable with 2‐N‐butylamine‐, 2‐N‐cyclohexylamine‐ and 2‐(N‐piperidyl)‐substituted nitropyridines, whose1H and13C NMR spectra were also determined. In the case of the secondary amines, a hydrogen bond between the amino proton and the 3‐nitro group was clearly detected.1H and13C NMR spectra of 2,6‐dinitro‐, 2,4‐dinitro‐ and 2,4,6‐trinitro‐2‐R‐benzenes (R = OCH3, NHC4H9, NH‐cyclo‐C6H11, NC5H10) were also recorded and compared with those of the pyridine derivatives. The electronic aza and nitro group effects are