Cystal structre of 5-hy-droxy-2-nitro-benzaldehyde.

In the title compound, C7H5NO4, the nitro group and the aldehyde group are inclined to the benzene ring by 16.6 (3) and 15.6 (3)°, respectively. In the crystal, mol-ecules are linked via O-H⋯O hydrogen bonds, forming chains along [100]. The chains are linked by C-H⋯O hydrogen bonds, forming a three-dimensional structure.