Molecular and crystal structures of the products of crystallization of (N′-furfurylidene)isonicotinoylhydrazide from aqueous solutions of hydrochloric and acetic acids

Crystals of (N′-furfurylidene)isonicotinoylhydrazide (I), which have been isolated from a water-methanol solution of hydrochloric acid (Ia) and an aqueous solution (∼50%) of acetic acid (Ib), are studied by X-ray diffraction. In Ia, the nitrogen atom of the pyridine ring is protonated. In the crystal, the intermolecular C=O⋯HN(Py) hydrogen bonds link the I · H+ cations into chains which are bound through centrosymmetric NH⋯W⋯Cl−⋯W′⋯H′N′ bridges. In molecule Ib, no protonation occurs; however, its pyridine N atom is blocked by the hydroxyl H atom of a solvate molecule of acetic acid. Crystals Ib have a layered structure. The crystallization water molecule is involved in the formation of three intermolecular hydrogen bonds, namely, those with the H atom of the amide group and the carbonyl O atoms of molecule I and an acetic acid molecule of the neighboring layer.