Polymorph Generation in Capillary Spaces:  The Preparation and Structural Analysis of a Metastable Polymorph of Nabumetone

Crystallization studies of nabumetone (4-(6-methoxy-2-naphthalenyl)-2-butanone) performed in capillary tubes yielded a metastable polymorph. The single-crystal X-ray structure of this high-energy form is presented and compared to the structure of the known low-energy form. The metastable form of nabumetone readily converts to the low-energy form in the solid state upon grinding or seeding with the low-energy polymorph. The instability of the metastable form is believed to be due to the presence of weaker C−H···O interactions when compared to the thermodynamically more stable form.