Solid State Synthesis of the 1:1 Mole Pharmaceutical Co-Crystal of Naproxen and Caprolactam

Pharmaceutical co-crystals represent an attractive opportunity in terms of pharmaceutical form and formulations. Co-crystallization affords the modification of the physical properties of an active pharmaceutical ingredient using a supramolecular approach. Herein we explore systematic solvent-drop grinding as a method of achieving co-crystal formation. The 1:1 pharmaceutical co-crystal of naproxen and caprolactam was initially prepared via solvent drop grinding and characterized using X-ray powder diffraction and infrared spectroscopy. The single crystals were subsequently obtained from solution. The 1:1 naproxen and caprolactam co-crystal exhibits the anticipated two point recognition carboxylic acid---amide supramolecular heterosynthon.