2-(3,4-Dichloro­phen­yl)-N-(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)acetamide

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 R₂²(10) type, while the third mol­ecule forms such dimers with itself. C—H...O inter­actions link the dimers.

(E)-N'-(4-Fluoro­benzyl­idene)-2-(3-methyl­phen­yl)acetohydrazide

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 R₂²(18) ring motifs, link the mol­ecules into dimers, which form columns along [010].

N-(4-Bromo­phen­yl)acetamide: a new polymorph

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.