Erratum: 2-acetamido-4,5-dinitrotoluene: A test molecule for the CCDC 'Blind structure prediction test, 2004 (Acta Crystallographica Section E: Structure Reports Online (2012). E68 (e18) DOI: 10.1107/S1600536812039670)

The name of one of the authors in the paper by Watkin et al. [Acta Cryst. (2004), E60, o2295–o2297] is corrected

N-(2-methyl-3,6-dinitrophenyl)acetamide

The structure of the title compound, C9H9N 3O5, was determined as one of a group of five related compounds in order to assess its suitability as a test material for the 2004 Cambridge Crystallographic Data Centre 'Blind Structure Prediction Test'. The structure consists of hydrogen-bonded ribbons of molecules stacked along the a axis with the benzene rings parallel by unit-cell translations. © 2005 International Union of Crystallography Printed in Great Britain - all rights reserved

2-Acetamido-4-nitrotoluene

The structure of the title compound, C9H10O 3, was determined as one of a group of five related compounds in order to assess its suitability as a test material for the 2004 Cambridge Crystallographic Data Centre 'Blind Structure Prediction Test'. The molecules are almost planar except for the acetamide group, which is involved in hydrogen bonding. The structure consists of columns of molecules hudrogen bonded into chains parallel to the c axis. © 2005 International Union of Crystallography Printed in Great Britain - all rights reserved

3-Iodo-2,6-dinitrotoluene

The structure of the title compound, C7H5IN 2O4, was determined as one of a group of five related compounds, in order to assess its suitability as a test material for the 2004 Cambridge Crystallographic Data Centre 'Blind Structure Prediction Test'. The crystal structure consists of columns of nearly planar molecules stacked parallel to the a axis, with an interplanar spacing of 3.478 (3) Å. © 2005 International Union of Crystallography Printed in Great Britain - all rights reserved

Search for a predicted hydrogen bonding motif - a multidisciplinary investigation into the polymorphism of 3-azabicyclo[3.3.1]nonane-2,4-dione

The predictions of the crystal structure of 3-azabicyclo[3.3.1]nonane-2,4-dione submitted in the 2001 international blind test of crystal structure prediction (CSP2001) led to the conclusion that crystal structures containing an alternative hydrogen bonded dimer motif were energetically competitive with the known catemer-based structure. Here we report an extensive search for a dimer-based crystal structure. Using an automated polymorph screen a new catemer-based metastable polymorph (form 2) and two new catemer-based solvates were found, and concurrent thermal studies reproduced form 2 and identified a plastic phase (form 3), whose powder X-ray diffraction pattern was consistent with the cubic space group I23 (a = 7.5856(1) Å). Computational studies on the monomer showed that the imide N−H was a weak hydrogen bond donor, rationalizing the occurrence of the plastic phase which involved the breaking of all hydrogen bonds, and modeling of small clusters showed that dimers could easily reorganize to give the catemer. FTIR spectra confirmed the weakness of the hydrogen bond, with the solute showing no self-assembly in solution. It is concluded that the weakness of the N−H donor, coupled with the globular shape of the molecule, allows unusually facile transformation between alternative hydrogen bonding motifs during aggregation and nucleation