Investigation of Benzimidazoles. 5. Transmission of the Substituent Effects in 2-Substituted 5(6)-Nitrobenzimidazoles Studied by 1H, 13C and 15N NMR Spectroscopy

Article abstract of DOI:10.1002/mrc.1260230505

The influence of substituents on the 1H, 13C and 15N NMR chemical shifts of 2-substituted 5(6)-nitrobenzimidazoles and their analogues labelled with 15N in the nitro group was investigated.It was found that the substituent effects are transmitted to the carbon and hydrogen nuclei in position 4-7 mainly by the resonance mechanism, but to the nitro-nitrogen atom with approximately equal contributions from the resonance and inductive components.Comparision of the transmission of substituent effect in nitrobenzimidazoles with para and meta derivatives of nitrobenzene showed that the nitro group seems to be more tightly conjugated with the benzimidazole fragment than with the benzene ring.