Co-crystallization of N'-benzylidenepyridine-4-carbohydrazide and benzoic acid via autoxidation of benzaldehyde

The 1:1 co-crystal N'-[(2-methylphenyl)methylidene]pyridine-4-carbohydrazide-benzoic acid (1/1), C13H11N3O center dot C7H6O2, formed unexpectedly after autoxidation of benzaldehyde during the slow evaporation process of a solution of isoniazid in benzaldehyde. The original intent of the synthesis was to modify isoniazid with benzaldehyde and crystallize the product in order to improve efficacy against Mycobacteria species, but benzoic acid formed spontaneously and co-crystallized with the intended product, N'-benzylidenepyridine-4-carbohydrazide.

Automated summary

In this study, the unexpected formation of a 1:1 co-crystal compound was observed during the modification of isoniazid for improved efficacy against Mycobacteria species. The co-crystal formation occurred due to the spontaneous generation of benzoic acid during the autoxidation of benzaldehyde.