Crystal and Molecular Structure and Stability of Isoniazid Cocrystals with Selected Carboxylic Acids

Reaction of isoniazid with benzoic acid, sebacic acid,
suberic
acid, and cinnamic acid results in formation of cocrystals. Two polymorphs
of isoniazid–suberic acid and two polymorphs of isoniazid–cinnamic
acid cocrystals were isolated. Crystal structure analysis shows the
presence of a pyridine–carboxylic acid synthon in the studied
cocrystals. The hydrazide group of isoniazid participates in N–H···O
and N–H···N hydrogen bond formation, producing
different supramolecular synthons. The stability study of isoniazid
cocrystals has been performed over a 22 week period. A comparison
of melting points of isoniazid–dicarboxylic acid 2:1 cocrystals
shows the decrease of melting point with an increasing length of the
acid. Solubility of isoniazid–carboxylic acid cocrystals tends
to increase with increasing solubility of the acid.