title: 5-Iodouracil: structure of a reflection twin.
abstract: The crystal structure of 5-iodouracil, C4H3IN2O2, has been determined in the noncentrosymmetric space group P21 on a nonmerohedrally twinned crystal. Both twin components are enantiomorphically pure, but the twin element is a mirror plane perpendicular to c*. The molecular structure is discussed and stacking faults in the two-dimensional packing are proposed as a reason for the twinning.
authors.affiliation: Bijvoet Center for Biomolecular Research, Crystal and Structural Chemistry, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
authors.forename: Martin
authors.initials: M
authors.lastname: Lutz
authors.affiliation: Bijvoet Center for Biomolecular Research, Crystal and Structural Chemistry, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
authors.forename: Thomas J S de
authors.initials: TJ
authors.lastname: Klein
authors.affiliation: Bijvoet Center for Biomolecular Research, Crystal and Structural Chemistry, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
authors.forename: Jeroen
authors.initials: J
authors.lastname: Huijben
keywords: 5-iodouracil; crystal structure; enantiomorphic purity; nonmerohedrally twinned crystal; stacking faults