No abstract

In the title compound (systematic name: 4-bromoacetyl-1,2,3-oxadiazol-3-ylium-5-olate), C10H7BrN2O3, the 1,2,3-oxadiazole ring and bromo­acetyl group are essentially planar [maximum deviation = 0.010 (4) and 0.013 (3) Å respectively] and form dihedral angles of 59.31 (19) and 67.96 (11)°, respectively, with the phenyl ring. The 1,2,3-oxadiazole ring is twisted slightly from the mean plane of the bromo­acetyl group, forming a dihedral angle of 9.16 (24)°. In the crystal, mol­ecules are linked by pairs of weak C—H⋯O hydrogen bonds into inversion dimers with R 2 2(12) ring motifs. The dimers are further connected by weak C—H⋯O hydrogen bonds into an infinite tape parallel to the b axis. In addition, π–π stacking inter­actions [centroid–centroid distance = 3.6569 (19) Å] and short inter­molecular contacts [O⋯O = 2.827 (3) and C⋯C = 3.088 (5) Å] are observed.

In the title compound, C13H16N2O4, an intra­molecular N—H⋯O hydrogen bond generates an S(6) ring. The mol­ecule adopts an E configuration with respect to the central C=N double bond. In the crystal, symmetry-related mol­ecules are connected into chains along [010] via weak C—H⋯N hydrogen bonds. The crystal structure is further stabilized by weak C—H⋯π inter­actions.

In the title compound, C15H10Br2Cl2O, the terminal benzene rings make a dihedral angle of 31.1 (2)° with each other. In the crystal, mol­ecules are stacked along the a axis and consolidated by C—H⋯π inter­actions. Short Cl⋯Cl [3.1140 (17) Å] and Br⋯Cl [3.4565 (13) Å] contacts are observed.

In the title compound, C12H11Cl3N2O4, the dihedral angle between the aromatic ring and the hydrazine (NH—N=C) grouping is 52.2 (3)°. The butanedioate groups exhibit planar conformations. An intra­molecular N—H⋯O hydrogen bond links the N—H group of the hydrazine to one of the meth­oxy groups of the butane­dioate moiety. In the crystal, mol­ecules are linked by C—H⋯O hydrogen bonds and π–π inter­actions are also observed [centroid–centroid separation = 3.535 (1) Å].