(E)-Methyl N′-[1-(2-hydroxy­phen­yl)ethyl­idene]hydrazinecarboxyl­ate

The mol­ecule of the title compound, C10H12N2O3, adopts a trans configuration with respect to the C=N bond. The dihedral angle between the benzene ring and the hydrazinecarboxyl­ate plane is 8.98 (7)°. Intra­molecular O—H⋯N and C—H⋯N hydrogen bonds are observed. Mol­ecules are linked into chains along the c axis by N—H⋯O hydrogen bonds. In addition, C—H⋯π inter­actions are observed

(E)-Ethyl N′-[1-(2-hydroxy­phen­yl)ethyl­idene]hydrazinecarboxyl­ate

In the mol­ecule of the title compound, C11H14N2O3, the dihedral angle between the benzene ring and the hydrazinecarboxyl­ate mean plane is 3.65 (12)°. Intra­molecular C—H⋯N and O—H⋯N hydrogen bonds result in the formation of a nearly planar six-membered ring, which is oriented at a dihedral angle of 2.38 (3)° with respect to the benzene ring, and a five-membered ring having an envelope conformation. In the crystal structure, inter­molecular N—H⋯O and C—H⋯N hydrogen bonds link the mol­ecules. There is a C—H⋯π contact between the benzene ring and the methyl group of the ethyl substituent

2′-(3-Hydroxy­benzyl­idene)pyrazine-2-carbohydrazide monohydrate

The title compound, C12H10N4O2·H2O, was synthesized by the reaction of pyrazine-2-carboxylic acid hydrazide and 3-hydroxy­benzaldehyde in ethanol. In the crystal structure, the organic mol­ecules are linked into extended chains by inter­molecular N(amide)—H⋯O(hydr­oxy) hydrogen bonds. Additional hydrogen bonds between the water mol­ecule and three adjacent organic mol­ecules, as well as face-to-face π–π stacking inter­actions between the benzene and pyrazine rings [centroid-to-centroid separation = 3.669 (2) Å and offset = 1.362 Å], link the mol­ecules into a three-dimensional framework

(E)-Ethyl N′-(4-bromo­benzyl­idene)hydrazinecarboxyl­ate

The title compound, C10H11BrN2O2, crystallizes with two independent mol­ecules in the asymmetric unit, in which the dihedral angles between the benzene ring and the hydrazine carboxylic acid mean plane are 3.0 (4) and 45.3 (3)°. The mol­ecules are linked into a one-dimensional network by inter­molecular N—H⋯O hydrogen bonds

(E)-Ethyl N′-(2-hydroxy­benzyl­idene)­hydrazinecarboxyl­ate

There are two mol­ecules in the asymmetric unit of the title compound, C10H12N2O3, with identical conformations. Each independent mol­ecule is approximately planar and adopts a trans configuration with respect to the C=N double bond. Intra­molecular O—H⋯N hydrogen bonds are observed in both mol­ecules. The mol­ecules are linked into a ribbon-like structure running along the b axis by inter­molecular N—H⋯O and C—H⋯O hydrogen bonds. The ribbons are arranged into layers parallel to (02)

Ethyl N′-[(E)-4-hydroxy­benzyl­idene]hydrazinecarboxyl­ate at 123 K

The mol­ecule of the title compound, C10H12N2O3, adopts a trans configuration with respect to the C=N bond. The dihedral angle between the benzene ring and the hydrazinecarboxyl­ate plane is 14.6 (1)°. Mol­ecules are linked into a three-dimensional network by O—H⋯O, N—H⋯O and C—H⋯O hydrogen bonds, and by C—H⋯π inter­actions

(E)-Methyl N′-(2-hydroxy­benzyl­idene)­hydrazinecarboxyl­ate at 123 K

In the title mol­ecule, C9H10N2O3, the hydrazinecarboxylic acid mean plane and the benzene ring form a dihedral angle of 11.1 (1)°. In the crystal structure, inter­molecular N—H⋯O hydrogen bonds link the mol­ecules into chains extending along the b axis. An intra­molecular O—H⋯N hydrogen bond is also present

2-[1-(3-Amino­phenyl­imino)­eth­yl]phenol

The title compound, C14H14N2O, exists as the enol–imine tautomer. A strong intra­molecular hydrogen bond between O and N atoms forms a six-membered ring with an S(6) graph-set motif, which is approximately coplanar with the phenol ring, the inter­planar angle being 3.4 (3)°. In the crystal, inter­molecular C—H⋯O hydrogen bonds and N—H⋯π inter­actions link the mol­ecules into infinite chains along [100]

2-[(E)-2-Hy­droxy-5-(trifluoro­meth­oxy)benzyl­idene­amino]-4-methyl­phenol

The title compound, C15H12F3NO3, is a Schiff base which adopts the cis-quinoid form in the solid state. The dihedral angle between the least-squares planes of the benzene rings being 3.6 (1)°. The F atoms of the –CF3 group are disordered over two sets of sites with refined occupancies of 0.61 (5) and 0.39 (5). An intra­molecular N—H⋯O hydrogen bond occurs. The crystal structure is stabilized by inter­molecular O—H⋯O hydrogen bonds