5-Amino-1-methyl-1H-benzimidazole.

The structure of the title compound, C(8)H(9)N(3), a potential anti-tumour drug, was determined in order to give more insight into its structure-function relationships. The benzimidazole core of the mol-ecule was found to be exactly planar, while the substituents are displaced slightly from the mol-ecular plane [C-C-N-C and C-C-C-N torsion angles of 0.8 (3) and 179.0 (1)° for the methyl and amino groups, respectively]. The bond lengths are analysed in detail and compared with those of the parent unsubstituted analogues. The results show that the lone-pair electrons on the amino N atom are involved in conjugation with the adjacent π system and hence affect the charge distribution in the heterocycle. Two inter-molecular N-H⋯N and C-H⋯N hydrogen bonds have been identified.