Collect. Czech. Chem. Commun. 1985, 50, 2443-2452

The wavenumbers of NO2 stretching vibrations and transmission of substituent effects in 2- and 4-substituted 3-nitropyridine series

Alexander Perjéssya, Danuta Rasalab, Piotr Tomasikc and Ryszard Gawineckib

a Department of Organic Chemistry, Comenius University, 842 15 Bratislava, Czechoslovakia
b Institute of Chemistry, Pedagogical University, 25 020 Kielce, Poland
c Department of Chemistry and Physics, The Hugon Kollataj Academy of Agriculture, 30 059 Krakow, Poland


The wavenumbers of both the symmetric and asymmetric stretching vibrations of the nitro group were measured in chloroform for the series of 2-X- and 4-X-substituted 3-nitropyridines as well as for o-X-substituted nitrobenzenes. The νas(NO2) and νs(NO2) values of both nitropyridine series were compared with those of corresponding nitrobenzenes. It has been found that the substituent effects in pyridines are transmitted to the 3-nitro group more readily from the 4-position, than from the 2-position. This transmission in 2-X-substituted 3-nitropyridines is comparable with that in the series of o-substituted benzene analogues. The transmission factors, γ, were determined according to Charton's definition for both 2,3- and 4,3-disubstituted pyridine rings. The separation of overall substituent effect into its inductive (field), resonance and steric components is discussed in terms of multiparameter correlation equations for wavenumber of asymmetric NO2 stretching vibration.