Crystal structure refinement of nitroguanidine

The crystal and molecular structure of nitroguanidine was refined using X-ray single-crystal diffraction methods. Previous structure determinations achieved with single crystal photographic or neutron powder techniques yielded values for the C-N 'formal' double bond-length that either equaled or exceeded the 'formal' C-N single-bond lenghts. Bond lengths were more precisely and accurately determined here than in the previous studies, but the 'formal' double-bond length still exceeds the 'formal' single bond lengths. Comparisons of crystal bond lengths with ab initio derived bond lengths of an isolated nitroguanidine molecule and hydrogen-bonded clusters of nitroguanidine molecules suggest that observed bond-length abnormalities are caused by intermolecular forces in the crystal. The crystal is orthorhombic, with a = 17.6390(5), b = 24.8730(7), c = 3.5903(1) Angstrom, V = 1575.19 Angstrom(3), Z = 16, and D-calc = 1.736 g cm(-3).