2-(2,4-Dichloro-phen-yl)acetic acid.

In the title compound, C(8)H(6)Cl(2)O(2), the dihedral angle between the C-C(=O)-OH carboxyl unit and the benzene ring is 70.70 (4)°. In the crystal, mol-ecules are linked into inversion dimers by pairs of O-H⋯O hydrogen bonds. The dimers are linked into chains extending along [001] by weak C-H⋯Cl inter-actions.

2-Methyl-3-p-tolyl-3H-benzo[e]indole-1-carbonitrile.

In the title compound, C(21)H(16)N(2), the dihedral angle between the benzoindole and tosyl ring systems is 71.99 (7)°. In the crystal, mol-ecules are linked into centrosymmetric dimers by pairs of C-H⋯N hydrogen bonds, generating R(2) (2)(16) loops.

2-mesitylacetic Acid.

In the title compound, C(11)H(14)O(2), the dihedral angle between the CCOO carboxyl unit and the benzene ring is 85.37 (7)°. In the crystal, the mol-ecules are linked into inversion dimers by pairs of O-H⋯O hydrogen bonds.

1-Meth-oxy-2-methyl-1H-benzo[f]indole-3-carbonitrile.

Apart from the methyl group of the meth-oxy fragment, the title compound, C(15)H(12)N(2)O, is almost planar (r.m.s. deviation = 0.045 Å); the C atom deviates from the mean plane by 1.216 (1) Å. In the crystal, π-π stacking [shortest centroid-centroid separation = 3.4652 (10) Å] and C-H⋯π inter-actions occur.