2-(7-Methyl-1H-indol-3-yl)acetonitrile.

In the title compound, C(11)H(10)N(2), the carbonitrile group is twisted away from the indole plane [C(cy)-C(me)-C(ar)-C(ar) = 66.6 (2)°; cy = cyanide, me = methyl-ene and ar = aromatic]. In the crystal, N-H⋯N hydrogen bonds link the mol-ecules into C(7) chains propagating in the [001] direction.

2-(4-Meth-oxy-1H-indol-3-yl)acetonitrile.

In the title compound, C(11)H(10)N(2)O, the cyanide group is twisted away from the indole-ring plane [C(cy)-C(me)-C(ar)-C(ar) = 70.7 (2)°; cy = cyanide, me = methyl-ene, ar = aromatic], whereas the meth-oxy C atom is almost coplanar with the ring system [displacement = 0.014 (5) Å]. In the crystal, N-H⋯N hydrogen bonds link the mol-ecules into C(7) chains propagating in [100].

2-(4-Chloro-1H-indol-3-yl)acetonitrile.

The title compound, C(10)H(7)ClN(2), contains two approximately planar mol-ecules, A and B (r.m.s. deviations = 0.039 and 0.064 Å, respectively) in the asymmetric unit. In the crystal, N-H⋯N hydrogen bonds link the mol-ecules into C(7) chains of alternating A and B mol-ecules propagating along the a-axis direction. The crystal used for the data collection was found to be a racemic twin.

4-Nitro-isophthalic acid.

In the crystal structure of the title compound, C(8)H(5)NO(6), both carboxyl groups are involved in inter-molecular centrosymmetric cyclic O-H⋯O hydrogen-bonding associations, which give a zigzag chain structure extending along (2[Formula: see text]1). Weak π-π stacking inter-actions are also present [minimum ring centroid separation = 3.893 (4) Å].

5-Methyl-1,2-oxazole-3-carb-oxy-lic acid.

In the crystal structure of the title compound, C(5)H(5)NO(3), all the non-H atoms are approximately coplanar: the carb-oxy O atoms deviating by 0.013 (2) and -0.075 (2) Šfrom the isoxazole ring plane. In the crystal, the molecules form inversion dimers linked by pairs of O-H⋯O hydrogen bonds and the dimers stack via π-π inter-actions [centroid-centroid distance = 3.234 (2) Å].

6-Methyl-nicotinic acid.

All non-H atoms of the title compound, C(7)H(7)NO(2), are nearly coplaner, the r.m.s. deviation being 0.0087 Å. In the crystal, the partially overlapped arrangement and the face-to-face distance of 3.466 (17) Šbetween parallel pyridine rings of neighboring mol-ecules indicates the existence of π-π stacking. Inter-molecular O-H⋯N hydrogen bonding and weak C-H⋯O hydrogen bonding are present in the crystal structure.

2,4-Dibromo-6-[(hydroxyimino)methyl]phenol.

In the title compound, C(7)H(5)Br(4)NO(2), intra-molecular O-H⋯N hydrogen bonds are observed. In the crystal structure, inter-molecular O-H⋯O hydrogen bonds link the mol-ecules into dimers.