Interactions between Isoniazid and α-Hydroxycarboxylic Acids

The present study refers to the preparation of isonicotinic acid hydrazide (isoniazid (INH)) cocrystals with two α-hydroxycarboxylic acids. The interaction of glycolic acid (H2ga) or dl-mandelic acid (H2ma) resulted in the formation of cocrystals, or salts of composition, as isoniazid−glycolic acid cocrystal (INH)·(H2ga) (1) and isoniazid−dl-mandelic acid salt cocrystal [HINH]+[Hma]−·(H2ma) (2), when reacted with isoniazid. An N’-(propan-2-ylidene)isonicotinic hydrazide hemihydrate, (pINH)·1/2(H2O) (3), was also prepared by condensation of isoniazid with acetone in the presence of glycolic acid. The prepared compounds were well characterized by elemental analysis and spectroscopic methods, and their three-dimensional molecular structure was determined by single-crystal X-ray crystallography. Hydrogen bonds involving carboxylic acid occur consistently with the pyridine ring N atom of the isoniazid and its derivatives. The remaining hydrogen-bonding sites on the isoniazid backbone vary on the basis of the steric influences of the derivative group. These are contrasted in each of the molecular systems.