A new polymorph of the common coformer isonicotinamide

A sixth polymorph of isonicotinamide was serendipitously discovered during an attempt to co-crystallize allopurinol with isonicotinamide in chloroform. A single crystal X-ray diffraction study indicated that this form crystallizes in the orthorhombic space group Pca2₁ and its uniqueness was further confirmed by comparison with the crystal structures of the other five known forms of isonicotinamide. Further characterization of the new polymorph included thermal analysis.