Chloranilic acid: a redetermination at 100†K.

The crystal structure of chloranilic acid, C(6)H(2)Cl(2)O(4), was first described by Andersen in 1967 [Andersen, E. K. (1967). Acta Cryst. 22, 188-191] at room temperature using visually estimated intensities. Taking into account the importance of the title compound, we have redetermined the structure at 100†(1)†K. The approximately planar mol-ecule [the maximum deviation from the mean plane through the ring is 0.0014†(9)†à for the ring atoms and 0.029†(3)†à for the other atoms] occupies a special position, lying across the center of symmetry. In the crystal structure, a two-dimensional hydrogen-bonded network sustained by O-H⋯O inter-actions runs approximately parallel to [101]. The two-dimensional layers are further packed in a parallel fashion, stabilized by Cl⋯Cl inter-actions [Cl⋯Cl = 3.2838†(8)†à , C-Cl⋯Cl = 152.96†(6)°].