X-ray crystal structure of dichloropicric acid

Dichloropicric acid is orthorhombic, space groupP212121; at 24°a=5.672(3),b=8.044(3),c=22.491(7) Å,Dx=1.929(2) g-cm−3,V=1026(1) Å3,Z=4. The phenolic OH group is intramolecularly hydrogen bonded to one of theortho nitro groups with an O...O distance of 2.524(5) Å. As a consequence, this nitro group is twisted out of the plane of the benzene ring by only 20.1° in spite of crowding by the adjacent chlorine atom which is only 2.764(3) Å from the O atom in the nitro group. The two non-hydrogen bonded nitro groups have twist angles of 73.9 and 84.1°. There is no evidence of intermolecular hydrogen bonding with any adjacent dichloropicric acid molecule.