Pitfalls of data mining: triclinic polymorph of 2,2-aziridinedicarboxamide revisited.

Several procedures have been employed for validating structural models refined on poor quality single-crystal diffraction data. Analysis of intra- and intermolecular distances in the structures of 2,2-aziridinedicarboxamide polymorphs proved to be a robust means, and a means independent of the chosen unit cell and symmetry, of detecting several incorrect atom-type assignments in the reported structure of the triclinic polymorph of 2,2-aziridinedicarboxamide [Brückner (1982). Acta Cryst. B38, 2405-2408]. The corrected model, refined in the space group P1, rules out the existence of any conformational polymorphism in this compound. Small differences in the powder-diffraction patterns calculated for the original and corrected structures of the triclinic polymorph illustrate the sensitivity of the above method for polymorph validation.