Heterocyclic tautomerism. V. 2-Guanidinobenzimidazole

A single-crystal X-ray structure analysis of 2-guanidinobenzimidazole shows the molecule exists in the solid state as tautomer 1 , with an intramolecular hydrogen bond between the benzimidazole-N3 and a guanidino-NH₂. The guanidino group is inclined at an angle of 13.8° to the benzimidazole plane. Other nitrogen atoms and their attached hydrogens are involved in additional intermolecular hydrogen bonds that connect the molecules in a complex three-dimensional network.