Ethyl 2-oxo-3-(3-phthalimidoprop-yl)-2,3-dihydro-1H-1,3-benzimidazole-1-carboxyl-ate.

In the title compound, C21H19N3O5, the phthalimide and benzamidazole ring systems are linked by a propyl chain. The benzamidazole unit also carries an eth-oxy-carbonyl substit-uent. The phthalimido and benzimidazole ring systems are essentially planar, the maximum deviations from their mean planes being 0.008 (2) and 0.020 (2) Å, respectively. The two ring systems are almost orthogonal to one another, making a dihedral angle of 82.37 (8)°. In the crystal, C-H⋯O hydrogen bonds and C-H⋯π contacts stack the mol-ecules along the b axis.

1-(4-Methyl-benz-yl)-1H-benzimidazol-2(3H)-one.

In the title compound, C15H14N2O, the fused five- and six-membered ring system is essentially planar, the maximum deviation from the mean plane being 0.009 (1) Å. The benzimidazol-2(3H)-one residue is nearly perpendicular to the benzyl ring, forming a dihedral angle of 77.41 (6)°. In the crystal, inversion dimers are formed by pairs of N-H⋯O hydrogen bonds; these dimers are linked by weak C-H⋯O inter-actions into a two-dimensional array in the (102) plane.

1-Octyl-1H-benzimidazol-2(3H)-one.

In the title compound, C(15)H(22)N(2)O, the octyl group adopts an all-trans conformation. In the crystal, mol-ecules form centrosymmetric dimers with an R(2) (2)(8) graph-set motif, linked by pairs of N-H⋯O hydrogen bonds. In addition, C-H⋯O contacts are observed.

1-Dodecyl-1H-benzo[d]imidazol-2(3H)-one.

In the title compound, C(19)H(30)N(2)O, the fused ring system is essentially planar, the maximum deviation from the mean plane being 0.013 (2) Šfor the N atom bearing the dodecyl chain. The 1-dodecyl group is almost perpendicular to the 1H-benzo[d]imidazol-2(3H)-one plane as indicated by the dihedral angle of 82.9 (2)°between planes through the fused ring system and the first three C atoms of the chain. The C-C-C-C torsion angles (about ±179°) of the dodecyl group indicate an anti-periplanar conformation. In the crystal, inversion dimers are formed by pairs of N-H⋯O hydrogen bonds.

1-Allyl-1H-1,3-benzimidazol-2(3H)-one.

The fused five- and six-membered rings in the title compound, C(10)H(10)N(2)O, are approximately coplanar, with an r.m.s. deviation of 0.008 Å. The mean plane of the allyl group is roughly perpendicular to the mean plane of the 1,3-benzimidazol-2(3H)-one system, making a dihedral angle of 86.1 (2)°. In the crystal, each mol-ecule is linked to its symmetry equivalent partner by a pair of N-H⋯O and C-H⋯O hydrogen bonds.