Crystal structures and characterization of the polymorphs of (2-furyl)oxoacetamide

The solid-state behaviour of (2-furyl)oxoacetamide (I) has been reinvestigated and newly characterized by a variety of methods. Three polymorphic forms have been identified; two of them (Form I and II) have been characterized using thermal, spectroscopic and crystallographic techniques. The monoclinic Form II undergoes inhomogeneous melting with phase transformation to the orthorhombic Form I in the temperature range of 85-95 °C. Forms I and II have been structurally characterized by single-crystal X-ray diffraction. Form I crystallizes in the relatively rare space group Fdd2 with Z = 48 whereas Form II crystallizes in P2₁ with Z = 2. This polymorphic system presents a special challenge to computational efforts to crystal structure prediction.