A new polymorph of the title compound, C8H8BrNO, has been determined at 173 K in the space group P21/c. The previous room-temperature structure was reported to crystallize in the ortho­rhom­bic space group Pna21 [Andreetti et al. (1968 ▶). Acta Cryst. B24, 1195–1198]. In the crystal, mol­ecules are linked by N—H⋯O hydrogen bonds forming chains along [010]. Weak C—H⋯π inter­actions are also present.

In the title compound, C16H15FN2O, the dihedral angles between the benzene rings are74.7(8), 74.1 (1), 74.2 (7) and 74.3 (5)° in the four independent mol­ecules in the asymmetric unit. In the crystal, N—H—O hydrogen bonds involving the hydrazide and acetyl groups, which form R 2 2(18) ring motifs, link the mol­ecules into dimers, which form columns along [010].

In the title compound, C19H17Cl2N3O2, there are three mol­ecules (A, B and C) in the asymmetric unit and each differs in the conformation adopted. As a result of steric repulsion, the amide group is rotated with respect to both the dichloro­phenyl and 2,3-dihydro-1H-pyrazol-4-yl rings, making dihedral angles of 44.5 (2) and 56.2 (2)°, respectively in A, 51.1 (2) and 54.1 (2)° in B, and 53.8 (2) and 54.6 (2)° in C. The dihedral angles between the dichloro­phenyl and 2,3-dihydro-1H-pyrazol-4-yl rings are 54.8 (2), 76.2 (2) and 77.5 (2)° in mol­ecules A, B and C, respectively, while the 2,3-dihydro-1H-pyrazol-4-yl and phenyl rings make dihedral angles of 45.3 (2), 51.2 (2) and 42.8 (2)°, respectively. In the crystal, two of the mol­ecules are linked through N—H⋯O hydrogen bonding to an adjoining mol­ecule, forming dimers of the R 2 2(10) type, while the third mol­ecule forms such dimers with itself. C—H⋯O inter­actions link the dimers.

In the title compound, C25H23N3O2, the central benzene ring makes dihedral angles of 77.14 (8) and 87.7 (2)° with the terminal benzene rings and an angle of 1.9 (1)° with the pyrazolone ring. The benzene ring and the N atom of the pyrazole ring bearing the phenyl substituent are disordered over two sets of sites with an occupancy ratio of 0.71 (2):0.29 (2). The N atoms of the pyrazole ring have a pyramidal environment, the sums of the valence angles around them being 354.6 (3) and 352.0 (6)/349.5 (15)°. In the crystal, mol­ecules are packed into layers parallel to the ac plane. The other monoclinic polymorphic form was reported recently [Dutkiewicz et al. (2012 ▶). Acta Cryst. E68, o1324].

In the title compound, C10H8ClN3S, the dihedral angle between the mean planes of the benzene and imidazo[2,1-b][1,3,4]thia­diazole rings is 6.0 (9)°. In the crystal, mol­ecules are assembled by the formation of centrosymmetric dimers by π-stacking of the thia­diazole and benzene rings of neighboring mol­ecules [centroid–centroid distance = 3.6938 (11) Å] along [010].

In the crystal structure of the title compound, C19H17Cl2N3O2, the mol­ecules form dimers of the R 2 2(10) type through N—H⋯O hydrogen bonding. As a result of steric repulsion, the amide group is rotated with respect to both the dichloro­phenyl and 2,3-dihydro-1H-pyrazol-4-yl rings, making dihedral angles of 80.70 (13) and 64.82 (12)°, respectively. The dihedral angle between the dichloro­phenyl and 2,3-dihydro-1H-pyrazol-4-yl rings is 48.45 (5)° while that between the 2,3-dihydro-1H-pyrazol-4-yl and phenyl rings is 56.33 (6)°.

In the title compound, C19H17Cl2N3O2, the amide group is planar and, through N—H⋯O hydrogen bonding to an adjoining mol­ecule, forms dimers of the R 2 2(10) type. As a result of steric repulsion, the amide group is rotated with respect to both the dichloro­phenyl and 2,3-dihydro-1H-pyrazol-4-yl rings, making dihedral angles of 71.63 (11) and 57.93 (10)°, respectively. The dihedral angle between the dichloro­phenyl and 2,3-dihydro-1H-pyrazol-4-yl rings is 76.60 (10)° while that between the 2,3-dihydro-1H-pyrazol-4-yl and phenyl rings is 49.29 (7)°. The crystal structure also features weak C—H⋯O inter­actions.

In the title compound, C9H12N2O, the dihedral angle between the benzene ring and the mean plane of the acetohydrazide group is 88.2 (7)°. In the crystal, N—H⋯O hydrogen bonds and weak C—H⋯O inter­actions link the mol­ecules into infinite ribbons along [001].

In the title mol­ecule, C17H18N2O2, the benzene rings form a dihedral angle of 83.0 (7)°. In the crystal, N—H⋯O hydrogen bonds, in an R 2 2(8) graph-set motif, link mol­ecules into centrocymmetric dimers, and weak C—H⋯π inter­actions further link these dimers into columns in [100].

In the title compound, C8H9N3O3, the dihedral angle between the benzene ring and the acetohydrazide C—C(=O)—N—N plane [maximum deviation = 0.0471 (13) Å] is 87.62 (8)°. The nitro group is twisted by 19.3 (2)° with respect to the benzene ring. In the crystal, N—H⋯O hydrogen bonds link the mol­ecules into a double-column structure along the b axis.

There are two independent mol­ecules in the asymmetric unit of the title compound, C21H18BrFO3, in which the dihedral angles between the fluoro­phenyl and bromo­phenyl groups are 77.0 (1) and 85.8 (1)°. In one of the mol­ecules, two methine C—H groups of the cyclo­hexene ring are disordered over two sets of sites in a 0.53 (2):0.47 (2) ratio. In both mol­ecules, the atoms of the ethyl group were refined as disordered over two sets of sites with occupancies of 0.67 (2):0.33 (2) and 0.63 (4):0.37 (4). The cyclo­hexene rings have slightly distorted sofa conformations in both mol­ecules. In the crystal, C—H⋯O inter­actions link mol­ecules into chains along the b axis.

The asymmetric unit of the title compound, C19H16N2O3, contains two independent mol­ecules in which the dihedral angles between the naphthalene ring system and the benzene ring are 10.0 (1) and 35.3 (1)°. In the crystal, mol­ecules are linked by N—H⋯O and O—H⋯O hydrogen bonds, forming a two-dimensional framework parallel to (001). Weak C—H⋯O and C—H⋯N hydrogen bonds complete a three-dimensional network.

The asymmetric unit of the title compound, C22H22O4, consists of two independent mol­ecules (A and B). The cyclo­hexene rings adopt slightly distorted sofa conformations in both mol­ecules. The dihedral angles between the benzene rings are 74.16 (13) and 71.85 (13)° in mol­ecules A and B, respectively. In the crystal, weak C—H⋯O hydrogen bonds link the mol­ecules into a ribbon-like structure along the b axis. Weak C—H⋯π inter­actions are also observed.

The title compound, C21H17NO2, exists in an E conformation with respect to the C=C bond. The pyridine ring forms dihedral angles of 5.57 (7) and 82.30 (9)°, respectively, with the central benzene ring and the terminal phenyl ring. The dihedral angle between the benzene and phenyl rings is 87.69 (8)°. No significant inter­molecular inter­actions are observed.

In the title compound, C20H21N3O2S, the 2,3-dihydro-1H-pyrazole ring is nearly planar (r.m.s. deviation = 0.023 Å) and forms dihedral angles of 16.96 (6) and 38.93 (6)° with the benzene and phenyl rings, respectively. The dihedral angle between the benzene and phenyl rings is 55.54 (6)°. The mol­ecular conformation is consolidated by an intra­molecular C—H⋯O hydrogen bond, which forms an S(6) ring. In the crystal, inversion dimers linked by pairs of N—H⋯Op (p = pyrazole) hydrogen bonds generate R 2 2(10) loops. The dimers are linked by C—H⋯O hydrogen bonds into sheets lying parallel to (100).

In the title compound, C16H16BrNO, the dihedral angle between the benzene rings is 69.8 (2)°. In the crystal, N—H⋯O hydrogen bonds link the mol­ecules into C(4) chains propagating in [100]. Adjacent mol­ecules in the chains are also linked by C—H⋯O inter­actions which, along with the N—H⋯O hydrogen bonds, generate R 2 1(6) loops.

In the title compound, C11H9ClN2OS, the thia­zole ring is nearly planar (r.m.s. deviation = 0.003 Å) and forms a dihedral angle of 64.18 (7)° with the bezene ring. In the crystal, inversion dimers linked by pairs of N—H⋯Nt (t = thia­zole) hydrogen bonds generate R 2 2(8) loops.

In the title compound, C21H16BrFN2, the fluoro-substituted benzene ring is disordered over two orientations about the C—F bond and the C—C bond between the benzene and pyrazole groups with a site-occupancy ratio of 0.516 (8):0.484 (8). The central pyrazole ring [maximum deviation = 0.035 (3) Å] makes dihedral angles of 22.4 (2), 11.0 (2), 77.19 (16) and 7.44 (17)° with the two disorder components of the benzene ring, the bromo-substituted benzene ring and the phenyl ring, respectively. In the crystal, mol­ecules are linked into a layer parallel to the bc plane through C—H⋯π inter­actions.

The asymmetric unit of the title compound, C16H14ClN3OS, contains two independent mol­ecules (A and B) linked into dimers via N—H⋯N hydrogen bonds. The 1,3-benzothia­zol-2-yl ring system and the benzene ring form dihedral angles of 17.08 (8) and 8.63 (7)° in mol­ecules A and B, respectively.

In the title compound, C19H18BrFN2O, the benzene rings form dihedral angles of 5.38 (7) and 85.48 (7)° with the mean plane of the 4,5-dihydro-1H-pyrazole ring (r.m.s. deviation = 0.0849 Å), which approximates to an envelope conformation with the –CH2– group as the flap. The dihedral angle between the benzene rings is 82.86 (7)°. In the crystal, C—H⋯F and C—H⋯O hydrogen bonds link the mol­ecules to form inversion dimers and together these generate chains along [011]. The crystal packing also features C—H⋯π inter­actions.

In the title compound, C18H14BrNO, the naphthalene ring system [maximum deviation = 0.015 (3) Å] forms a dihedral angle of 67.70 (10)° with the benzene ring. In the crystal, mol­ecules are linked by N—H⋯O hydrogen bonds into C(4) chains propagating in [100]. A C—H⋯O inter­action reinforces the chain connectivity, generating an R 2 1(6) loop.

In the title compouund, C15H10F2O, the mol­ecule exists in an E conformation with respect to the C=C bond [1.3382 (16) Å]. The dihedral angle between the fluoro-substituted benzene rings is 6.80 (6)° and the whole mol­ecule is roughly planar (r.m.s. deviation for the non-H atoms = 0.069 Å). In the crystal, mol­ecules are linked by C—H⋯F and C—H⋯O inter­actions into sheets lying parallel to the bc plane.

The asymmetric unit of the title compound, C20H14Cl3NO, consists of two independent mol­ecules. In one mol­ecule, the chlorinated benzene ring forms dihedral angles of 12.00 (9) and 77.04 (9)° with the phenyl rings. The dihedral angle between the phenyl rings is 80.37 (10)°. The corresponding dihedral angles for the other mol­ecule are 26.34 (10), 62.98 (10) and 88.47 (11)°, respectively. One of the mol­ecules features an intra­molecular C—H⋯O hydrogen bond, which forms an S(6) ring motif. In the crystal, mol­ecules are linked by N—H⋯O hydrogen bonds into [100] chains. The chains are further linked by C—H⋯O and C—H⋯Cl hydrogen bonds into a three-dimensional network.

In the title compound, C17H15FN2O, the pyrazoline ring adopts a flattened envelope conformation. The dihedral angle between the fluoro-substituted benzene ring and the phenyl ring is 69.20 (5)°. In the crystal, a pair of C—H⋯O hydrogen bonds link neighbouring mol­ecules, forming an inversion dimer. The crystal structure is further consolidated by C—H⋯π inter­actions and by a π–π inter­action with a centroid–centroid distance of 3.7379 (6) Å.

The asymmetric unit of the title compound, C27H16F2N2O4, consists of two crystallographically independent mol­ecules (A and B). In mol­ecule B, the isoindoline-1,3-dione ring system is disordered over two set of sites with a site-occupancy ratio of 0.658 (12):0.342 (12). In mol­ecule A, the fluoro-substituted benzene rings make dihedral angles of 18.36 (8) and 46.37 (8)° with the central benzene ring, whereas the corresponding angles are 40.90 (8) and 52.89 (9)° in mol­ecule B. The isoindoline ring system in mol­ecule A and the major and minor components of the disordered isoindoline ring system in mol­ecule B make dihedral angles of 58.50 (4), 54.13 (16) and 70.01 (28) °, respectively, with their attached benzene rings, linked through the amide group. An intra­molecular O—H⋯O hydrogen bond generates an S(6) ring in each mol­ecule. In the crystal, mol­ecules are linked by N—H⋯O, C—H⋯F and C—H⋯O hydrogen bonds into sheets lying parallel to the bc plane. The crystal studied was a non-merohedral twin with a refined twin component ratio of 0.9316 (8):0.0684 (8).