Structural similarities among eight benzoylhydrazones

The crystal structures of eight benzoylhydrazones with different substituents have been investigated, namely 1-benzoyl-2-(propan-2-ylidene)hydrazone, C(10)H(12)N(2)O, (I), 1-benzoyl-2-(1-cyclohexylethylidene)hydrazone, C(15)H(20)N(2)O, (II), 1-benzoyl-2-[1-(naphthalen-2-yl)ethylidene]hydrazone, C(19)H(16)N(2)O, (III), 1-benzoyl-2-(1-cyclohexylbenzylidene)hydrazone, C20H22N2O, (IV), 1-benzoyl-2-(1-phenylbenzylidene)hydrazone, C(20)H(16)N(2)O, (V), 1-benzoyl-2-[1-(4-chlorophenyl)benzylidene]hydrazone, C(20)H(15)ClN(2)O, (VI), 1-benzoyl-2-(4-hydroxybenzylidene)hydrazone methanol monosolvate, C(14)H(12)N(2)O(2) · CH(3)OH, (VII), and 1-benzoyl-2-(1,1-diphenylpropan-2-ylidene)hydrazone, C(22)H(20)N(2)O, (VIII). The ten molecules in the eight crystal structures [there are two independent molecules in the structures of (V) and (VI)] show similar conformations and hydrogen-bonding patterns. The C=N-NH-C=O group is planar, but the plane of the phenyl ring of the benzoyl group is rotated by about 30° with respect to that of the keto group [except for (IV), where the groups are coplanar]. Only in the amide group of (VIII) is the N-H group syn to the C=O bond, whereas the seven other compounds exhibit the anti conformation. Unless prevented by steric hindrance, N-H...O hydrogen bonds help to stabilize the crystal structure, which leads to infinite chains or dimers depending upon the molecular conformation. The molecular packing is supported by intermolecular C-H...O interactions. In the crystal structure of (VII), the methanol solvent molecule participates in two strong hydrogen bonds and two weak C-H...O interactions, thus acting as a link between the molecular chains.