In the title mol­ecule, C13H7N3O8, the phenyl and benzene rings are rotated from the mean plane of the central ester group by 18.41 (9) and 81.80 (5)°, respectively. The dihedral angle between the rings is 80.12 (14)°. In the crystal, mol­ecules are linked by weak C—H⋯O inter­actions, forming helical chains along [010].

In the title compound, C21H18O4, the outer benzyl rings are disordered over two resolved positions in a 0.50 ratio. The O—CH2 groups form dihedral angles of 4.1 (2) and 10.9 (4)° with the central benzene ring, adopting a syn–anti conformation with respect to this ring. In the crystal, the mol­ecules are linked by O—H⋯O hydrogen bonds and weak C—H⋯O inter­actions, forming chains along [010].

In the title compound, C14H9N3O8, the benzene rings form a dihedral angle of 69.02 (5)°. The central ester group is rotated by 25.86 (9)° relative to the p-tolyl group. In the crystal, the mol­ecules are linked by C—H⋯O inter­actions into helical chains along [010].

In the title mol­ecule, C19H21BrN2O, the piperidone ring adopts a chair conformation with a total puckering amplitude Q T of 0.554 (2) Å. The dihedral angle between the benzene rings is 64.10 (7)°. There are no significant inter­molecular inter­actions.

In the title pyridine N-oxide derivative, C6H4N2O, the 4-cyano substituent almost lies in the mean plane of the pyridine ring (r.m.s deviation of all non-H atoms = 0.004 Å). This redetermination results in a crystal structure with significantly higher precision [N—O bond length is 1.2997 (15) compared with 1.303 (5) Å in the original] than the original determination, which was recorded using the multiple-film technique and visually estimated intensities [Hardcastle et al. (1974 ▶). J. Cryst. Mol. Struct. 4, 305–311]. The crystal structure features weak C—H⋯O and C—H⋯N inter­actions, which lead to the formation of chains that inter­sect each other parallel to (001).

In the title benzoate derivative, C14H9N3O8, the benzene rings form a dihedral angle of 87.48 (5)°. The central ester unit forms an angle of 19.42 (7)° with the methyl­benzene ring, indicating a significant twist. In the crystal, the mol­ecules are linked by weak C—H⋯O inter­actions forming a helical chain along [010].

The title compound, C12H10BrN3, is essentially planar (r.m.s. deviation of all non-H atoms = 0.0174 Å), with a dihedral angle of 0.5 (2)° between the two aromatic rings. In the crystal, mol­ecules are linked by weak N—H⋯N inter­actions, forming a zigzag chain running parallel to [001].

In the title compound, C16H16BrN, the tricyclic carbazole system is essentially planar (r.m.s. deviation of all non-H atoms = 0.010 Å). The dihedral angle between the two outer carbazole rings is 1.1 (3)°. There are no directional inter­molecular contacts in the crystal packing.

The asymmetric unit of the title compound, C16H13N3O2, contains two independent mol­ecules in which the pyridine and benzene rings form dihedral angles of 81.7 (2) and 79.8 (2)°, indicating the twist in the mol­ecules. In the crystal, weak C—H⋯N inter­actions link mol­ecules into chains along [100].

In the crystal structure of the title compound, C13H8BrNO4, mol­ecules are linked into chains along [101] by weak C—H⋯O hydrogen bonds and Br⋯O contacts [3.140 (4) Å]. The planes of the nitrated and brominated aryl rings form a dihedral angle of 64.98 (10)°, indicating a twist in the mol­ecule.

In the title compound, C14H11BrO2, an ester formed from the reaction of 4-methyl­phenol with 4-bromo­benzoyl­chloride, the dihedral angle between the benzene rings is 54.43 (7)°, indicating a twist in the mol­ecule. In the crystal, weak C—H⋯O inter­actions link the mol­ecules into supra­molecular layers in the bc plane, and these are connected along the a axis by Br⋯Br contacts [3.6328 (5) Å].

In the title mol­ecule, C10H11BrClNO, there is a twist between the mean plane of the amide group and the benzene ring [C(=O)—N—C—C torsion angle = −27.1 (3)°]. In the crystal, inter­molecular N—H⋯O and weak C—H⋯O hydrogen bonds link the mol­ecules into chains along [010].

In the title mol­ecule, C11H14BrNO2, there is twist between the mean plane of the amide group and the benzene ring [the C—N—C—C torsion angle is −172.1 (2)°]. The amide H atom forms an intra­molecular hydrogen bond with the Br atom. In the crystal, inter­molecular O—H⋯O and weak C—H⋯O hydrogen bonds link mol­ecules into a chain along [100].

In the title mol­ecule, C11H14BrNO, there is twist between the mean plane of the amide group and the benzene ring [C(=O)—N—C C torsion angle = −31.2 (5)°]. In the crystal, inter­molecular N—H⋯O and weak C—H⋯O hydrogen bonds link mol­ecules into chains along [100]. The methyl group H atoms are disordered over two sets of sites with equal occupancy.

The title compound, C10H11BrN2O3, exhibits a small twist between the amide residue and benzene ring [the C—N—C—C torsion angle = 12.7 (4)°]. The crystal structure is stabilized by weak N—H⋯O, C—H⋯Br and C—H⋯O inter­actions. These lead to supra­molecular layers in the bc plane.

The asymmetric unit of the title compound, C8H8O2, contains two crystallographically independent mol­ecules, which form dimers linked by O⋯H—O hydrogen bonds. The benzene rings in the dimers are inclined at a dihedral angle of 7.30 (8)° and both methyl groups display rotational disorder. This redetermination results in a crystal structure with significantly higher precision than the original determination [Ellas & García-Blanco (1963 ▶). Acta Cryst. 16, 434], in which the authors reported only the unit-cell parameters and space group, without any detailed information on the atomic arrangement. In the crystal, dimers are connected by weak C—H⋯O inter­actions, forming R 2 2(10) and R 4 4(18) rings along [110] and an infinite zigzag chain of dimers along the [001] direction also occurs.

The asymmetric unit of the title compound, C3H5N2 +·C6H2N3O7 −·C3H4N2·H2O or H(C3H4N2)2 +·C6H2N3O7 −·H2O, contains a diimidazolium cationic unit, one picrate anion and one mol­ecule of water. In the crystal, the components are connected by N—H⋯O, N—H⋯N and O—H⋯O hydrogen bonds, forming a two-dimensional network parallel to (001). In addition, weak inter­molecular C—H⋯O hydrogen bonds lead to the formation of a three-dimensional network featuring R 5 5(19) rings.

The title compound, C9H8O2S2, can be used as a chain transfer agent and may be used to control the behavior of polymerization reactions. O—H⋯O hydrogen bonds of moderate character link the mol­ecules into dimers. In the crystal, the dimers are linked into sheets by C—H⋯O inter­actions, forming R 4 2(12) and R 2 2(8) edge-fused rings running parallel to [101]. There are no inter­molecular inter­actions involving the S atoms.

In the title 2:1 adduct, C14H10O4S2·0.5C10H8N2O2, which arose from an unexpected oxidation of a precursor, the dihedral angle between the aromatic rings in the disulfide is 82.51 (11)°. In the crystal, the molecules are linked by O—H⋯O, O—H⋯N and C—H⋯O interactions, generating sheets.

In the title salt, C3H5N2 +·C7H6NO2 −, the carboxyl­ate group of the 4-amino­benzoate anion forms a dihedral angle of 13.23 (17)° with respect to the benzene ring. There are N—H⋯O hydrogen-bonding inter­actions between the anion and cation, and weak inter­molecular C—H⋯O contacts with carboxyl­ate O-atom acceptors of the 4-amino­benzoate anion result in extended three-dimensional R 4 4(22) and R 5 6(30) edge-fused rings along the [100], [010] and [001] directions.

In the title compound, C3H5N2 +·C4H3O4 −, the dihedral angle between the imidazolium ring and the plane formed by the fumarate anion is 80.98 (6)°. In the crystal structure, inter­molecular O—H⋯O and N—H⋯O hydrogen bonds form extended chains along [100] and [01], creating a two-dimensional network.

The title compound, C15H14O2, was obtained by Friedel–Crafts acyl­ation between 2,5-dimethyl­phenol and benzoyl chloride in the presence of aluminium chloride as a catalyst. The dihedral angle between the benzene rings is 61.95 (4)°. In the crystal, O—H⋯O hydrogen bonding and C—H⋯O weak inter­actions lead to polymeric C(6), C(8) and C(11) chains along the a, b and c-axis directions, respectively.

The title adduct, C7H5NO4·C6H6N2O3, forms part of an ongoing study of the design of non-centrosymmetric systems based on 3-methy-4-nitro­pyridine 1-oxide. The components of the adduct are linked by inter­molecular O—H⋯O hydrogen bonds. The rings of the two components are nearly planar, with a dihedral angle of 11.9 (2)° between the planes. The supra­molecular structure shows that mol­ecules of the title complex are linked into sheets by a combination of strong O—H⋯O and weak C—H⋯O hydrogen bonds.

In the title compound, C16H16BrN, the benzene rings are inclined to each other with a dihedral angle between their mean planes of 50.5 (3)° and the C=C bond adopts a cis conformation.

In the crystal of the title compound, C17H16N2, mol­ecules are linked by C—H⋯N hydrogen bonds, forming rings of graph-set motifs R 2 1(6) and R 2 2(10). The title mol­ecule is close to planar, with a dihedral angle between the aromatic rings of 0.6 (1)°. Torsion angles confirm a conformational trans structure.