Woehler and Liebig revisited: A small molecule reveals its secrets - The crystal structure of the unstable polymorph of benzamide solved after 173 years

In this work, we revisit the question of the metastable crystal form of benzamide. This was first identified in 1832 by Liebig and Woehler, but its structure has never been determined. It is shown how a combination of microscopic, spectroscopic, and diffraction techniques have been used to solve, finally, the structure of this highly metastable Form II of benzamide. The combination of morphology, disorder, and nucleation under highly labile conditions lead to some speculation as to the origins of such an unstable polymorph.