Molecular Conformation and Crystallization: The Case of Ethenzamide

Ethenzamide is a small, conformationally
labile pharmaceutical
molecule which crystallizes in an unusual conformation relative to
both its co-crystals and to similar molecules found in the Cambridge
Structural Database. Relative to its co-crystals, large ethenzamide
crystals are challenging to grow, a property which may be linked to
the crystal structure conformation. We have explored this link through
computational and spectroscopic techniques, studying the conformational
properties of the individual molecules in vacuo and
in solution. Structures built from alternative conformations have
been generated theoretically, but crystallizations under a wide range
of conditions have resulted in no new polymorph, though single crystal
structures for the known form and two new co-crystals have been solved.