Investigation of benzimidazoles. III—transmission of the substituent effects in 2‐substituted 1‐methylbenzimidazoles studied by ¹³C nuclear magnetic resonance

Abstract

Abstract The influence of substituents on the 13 C NMR chemical shifts of 2‐substituted 1‐methylbenzimidazoles has been investigated. The electronic effects of the substituents are transmitted to C‐4 and C‐7 mainly by the resonance mechanism, and to C‐5, C‐6 and N ‐CH 3 , by approximately equal contributions of the resonance and inductive components. A critical analysis of the share in the transmission of substituent effects through the ‘pyridine‐type’ and ‘pyrrole‐type’ nitrogen atoms is given.