2,2′-(4,6-Dinitro-1,3-phenylenedioxy)diacetic acid dihydrate

In the title compound, C10H8N2O10·2H2O, the skeleton of the dicarboxylic acid molecule is approximately planar, the largest deviation being 0.477 (1) Å for an O atom of a nitro group; this nitro group is twisted out of the plane of the ring by 24.6 (1)°. Adjacent molecules are linked by O—H⋯O hydrogen bonds, which connect the dicarboxylic acid and water molecules into a three-dimensional supramolecular network.

In the title compound, C 10 H 8 N 2 O 10 Á2H 2 O, the skeleton of the dicarboxylic acid molecule is approximately planar, the largest deviation being 0.477 (1) Å for an O atom of a nitro group; this nitro group is twisted out of the plane of the ring by 24.6 (1) . Adjacent molecules are linked by O-HÁ Á ÁO hydrogen bonds, which connect the dicarboxylic acid and water molecules into a three-dimensional supramolecular network.

Comment
Flexible aromatic carboxylic acid with oxygen is a kind of biological activity of the organic carboxylic acid, not only in agriculture, such as plant growth regulators and herbicides it is applied, but also it is important to the synthesis of some organic medicine centre body. Compared with other rigid carboxylic acid ligands, such flexible aromatic carboxylic acid have highly plasticity and spatial configuration of, so it provides a rich and colorful way to identify and assemble for constructing a novel topological network structure with the special physical and chemical properties (Coronado et al., 2000;Gao et al., 2006). In this paper, we report the synthesis and crystal structures of a new flexible aromatic carboxylic acid compound.
In the crystal structure, the skeletons of the dicarboxylic acid molecule is approximately co-planar with the largest deviation being 0.477 (1) Å from O7 of one twisty nitro group [dihedral angles = 24.6 (1)°] ( Figure 1).
There are six symmetry-independent 'active' H atoms in the crystal structure, all of them participate in hydrogen bonds, which link the dicarboxylic acid and water molecules into a three-dimensional supramolecular network ( Figure 2, Table 1).

Experimental
The synthesis of target product is as follows: chlorine acetic acid (51.6 g, 0.54 mol), sodalye (36.3 g, 0.90 mol) and resorcinol (20 g, 0.18 mol) were dissolved into 200 ml distilled water with stirring. The mixture was heated to refluxed for 6 h, then the pH value was adjusted to about 2.0 by using 3 M hydrochloric acid. After cooling to the room temperature, 10.8 g (27%) yellow precipitate was obtained. The 10.8 g above yellow product was dissolved into 100 ml concentrated sulfuric acid with stirring, and then the mixture of nitric acid (9.45 g, 0.15 mol) and sulfuric acid (20.58 g, 0.21 mol) was dropped into the above solution with keeping the reaction temperature under 0° C for 1 h. Then the rection solution is stirred about 5h at room temperature. The mixture was poured into 500 ml water solution, the crude product were obtained (37%). The product was suitable for X-ray test obtained by recrystallization from water solution.