The active pharmaceutical ingredient 2-chloro-4-nitrobenzoic acid (2c4n) is a potentially novel therapy for immunodeficiency diseases as an anti-viral and anti-cancer agent and is a dimorph in the solid state. 2c4n is a historically significant compound from a polymorphic point of view, as it was one of the samples used by Ebert and Gottlieb to show that polymorphs can be identified or differentiated through their IR spectra back in 1952[1].
[1] Andreas Lemmerer, Joel Bernstein, Catharine Esterhuysen. “Synthesis, characterization, and molecular modeling of a pharmaceutical co-crystal: (2-chloro-4-nitrobenzoic acid):(nicotinamide)?.” Journal of pharmaceutical sciences 99 9 (2010): 4054–4071.
