Polymorphism in 2-Chlorobenzamide: Run of the Mill or Not?

Structures of two very similar polymorphic forms of 2-chlorobenzamide have been obtained at low temperature. The metastable α-form is very susceptible to grinding, a property not initially realized considering the polymorphs have been reported in the literature for many years. Systematic milling studies have been carried out in a search for other polymorphic forms and to assess the rate of any polymorphic change(s). No new polymorphs were found, though a computational search for low energy structures suggested a complex crystal-energy landscape. An experimental polymorph screen was also carried out