Redetermination of cyclo-trimethylenetrinitramine

The redetermined structure of 1,3,5-trinitro-1,3,5-triazacyclohexane, C3H6N6O6, at 90 (2) K has orthorhombic (Pbca) symmetry. It is of interest with respect to energetic compounds. The structure was originally investigated through X-ray diffraction by Hultgren [(1936). J. Chem. Phys. 4, 84]. Later X-ray investigations were completed by McCrone [(1950). Anal. Chem. 22, 954-955] and Harris, Reed & Gluyas [(1959). AFOSR-TR-59-165 Ohio State University Research Foundation, Columbus, Ohio, USA]. A single-crystal neutron diffraction study was performed by Choi & Prince [(1972). Acta Cryst. B28, 2857-2862] to ascertain the H-atom positions, which had not been defined by the earlier X-ray diffraction studies. All previous studies were performed at or near room temperature. The structure provided is the alpha polymorph of the title compound. The ring atoms are arranged in the chair conformation with two nitro groups occupying pseudoequatorial positions and the remaining nitro group is axial. The crystal packing is stabilized by close intramolecular interactions from one H atom in each methylene group to O atoms of adjacent nitro groups, ranging from 2.251 to 2.593 angstrom.