Crystal structure ofN′-[(E)-3,5-dichloro-2-hydroxybenzylidene]-4-nitrobenzohydrazide dimethylformamide monosolvate

In the title compound, C14H9Cl2N3O4·C3H7NO, the hydrazone molecule adopts anEconformation with respect to azomethine bond, and the dihedral angle between the two aromatic rings [8.96 (11)°] shows that the rings are almost co-planar. The planar conformation of the molecule is stabilized by the intramolecular O—H...N hydrogen bond involving the OH group and azomethine N atom. The azomethine and keto bond distances [1.269 (2) and 1.210 (2) Å, respectively] are very close to the formal C=N and C=O bond lengths. The dimethylformamide solvent molecule is connected to the hydrazone NH groupviaan N—H...O hydrogen bond. In the crystal, non-classical C—H...O and C—H...Cl hydrogen bonds link the molecules into chains along [322]. A supramolecular three-dimensional architecture is created by weak C—Cl...π [4.163 (3) Å, 83.26 (9)°] and π–π [centroid–centroid distance = 4.0395 (14) Å] interactions.

Crystal structure of 4-{(E)-[2-(pyridin-4-ylcarbonyl)hydrazin-1-ylidene]methyl}phenyl acetate monohydrate

The asymmetric unit of the title compound, C15H13N3O3·H2O, comprises a 4-{(E)-[2-(pyridin-4-ylcarbonyl)hydrazinylidene]methyl}phenyl acetate molecule and a solvent water molecule linked by O—H...O and O—H...N hydrogen bonds from the water molecule and a C—H...O contact from the organic molecule. The compound adopts anEconformation with respect to the azomethine bond and the dihedral angle between the pyridine and benzene rings is 21.90 (7)°. The azomethine bond [1.275 (2) Å] distance is very close to the formal C=N bond length, which confirms the azomethine bond formation. An extensive set of O—H...O, O—H...N, N—H...O and C—H...O hydrogen bonds builds a two-dimensional network progressing along thecaxis.

Dichlorido{(2E)-2-[phenyl(pyridin-2-yl)methylidene]hydrazinecarbothioamide}cadmium(II) methanol monosolvate

In the title compound, [CdCl2(C13H12N4S)]·CH3OH, the coordination geometry of the CdIIion is slightly distorted square-pyramidal, as indicated by the τ index of 0.36 (8). The S atom, two N atoms from the pyridyl-azomethine moiety and one of the Cl atoms comprise the basal plane, while the other Cl atom occupies the apical position. The hydrazinecarbothioamide moiety adopts anEconformation with respect to the azomethine bond. The solvate molecule in the crystal lattice plays a major role in interconnecting adjacent molecules by means of O—H...Cl and N—H...O hydrogen-bonding interactions. A supramolecular three-dimensional architecture is sustained in terms of further N—H...Cl and C—H...Cl hydrogen-bonding interactions.

N′-[(E)-1-(2-Fluorophenyl)ethylidene]pyridine-4-carbohydrazide

The title compound, C14H12FN3O, adopts anEconformation with respect to the azomethine bond. The pyridyl and fluorobenzene rings make dihedral angles of 38.58 (6) and 41.61 (5)° respectively with the central C(=O)N2CC unit, resulting in a non-planar molecule. The intermolecular interactions comprise two classical N—H...O and N—H...N hydrogen bonds and four non-classical C—H...O and C—H...F hydrogen bonds. These interactions are augmented by a weak π–π interaction between the benzene and pyridyl rings of neighbouring molecules, with a centroid–centroid distance of 3.9226 (10) Å. This leads to a three-dimensional supramolecular assembly in the crystal system. The F atom is disordered over two sites in a 0.559 (3): 0.441 (3) ratio, through a 180° rotation of the fluorobenzene ring.

Study of acid hydrolysis of bromazepam

Quantitative study of an acid hydrolysis of bromazepam, which in acidic solution simultaneously undergoes reversible 4,5-azomethine bond cleavage and protolytic reactions, was performed (t = 25 °C). When an equilibrium is established, four species are simultaneously present in solution. Two approaches, both based on theoretically derived dependence between the absorbance (A) and the solution acidity ([H3O+]), were used to determine appropriate equilibrium constants. In the first, the least-squares method was used to fit experimentally obtained (A, [H3O+]) value pairs to a derived function. With values obtained as fitting parameters, the probability distribution for equilibrium constants was calculated with the virtual experiments performed using Monte Carlo simulations. In the second one, spectrophotometric analysis indicated an existence of two distinct pH intervals, both with three dominant species involved. Spectral data were used to calculate equilibrium constants by a linear curve fitting analysis. Values obtained for equilibrium constants from the numerical and the experimental approaches are in good accordance and were used to calculate distribution of all the species as a function of pcH. Key words: bromazepam, acid hydrolysis, equilibrium constants.