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

1985; Wiley-VCH; Volume: 50; Issue: 11 Linguagem: Inglês

10.1135/cccc19852443

1212-6950

Alexander Perjéssy, Danuta Rasała, Piotr Tomasik, Ryszard Gawinecki,

Chemical Reaction Mechanisms

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 ν as (NO 2 ) and ν s (NO 2 ) 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 NO 2 stretching vibration.