1,3-Bis(ethyl-amino)-2-nitro-benzene, 1,3-bis-(n-octylamino)-2-nitro- benzene and 4-ethylamino-2-methyl-1H-benz-imid-azole

1,3-Bis(ethyl-amino)-2-nitro-benzene, C10H15N3O2, (I), and 1,3-bis-(n-octylamino)-2-nitro-benzene, C22H39N3O2, (II), are the first structurally characterized 1,3-bis-(n-alkyl-amino)-2-nitro-benzenes. Both mol-ecules are bis-ected though the nitro N atom and the 2-C and 5-C atoms of the ring by twofold rotation axes. Both display intra-molecular N - H⋯O hydrogen bonds between the amine and nitro groups, but no inter-molecular hydrogen bonding. The nearly planar mol-ecules pack into flat layers ca 3.4 Å apart that inter-act by hydro-phobic inter-actions involving the n-alkyl groups rather than by π-π inter-actions between the rings. The intra- and inter-molecular inter-actions in these mol-ecules are of inter-est in understanding the physical properties of polymers made from them. Upon heating in the presence of anhydrous potassium carbonate in dimethyl-acetamide, (I) and (II) cyclize with formal loss of hydrogen peroxide to form substituted benzimidazoles. Thus, 4-ethylamino-2-methyl-1H-benzimidazole, C10H13N3, (III), was obtained from (I) under these reaction conditions. Compound (III) contains two independent mol-ecules with no imposed inter-nal symmetry. The mol-ecules are linked into chains via N - H⋯N hydrogen bonds involving the imidazole rings, while the ethylamino groups do not participate in any hydrogen bonding. This is the first reported structure of a benzimidazole derivative with 4-amino and 2-alkyl substituents.