4- and 5-nitro-2-benzoylbenzoic acid

The structures of two isomeric nitro 2-benzoylbenzoic acids have been determined. 4-Nitro-2-benzoylbenzoic acid, C₁₄H₉NO₅, monoclinic, P2₁/c, a = 9.455(5), b = 6.632(2), c = 21.333(7)Å, = 107.96(3)°, Z = 4, V = 1270.6(9)ų, 5-nitro-2-benzoylbenzoic acid, C₁₄H₉NO₅, monoclinic, P2₁/c, a = 10.201(6), b = 8.515(4), c = 14.573(7)Å, = 101.35(4)°, Z = 4, V = 1241.1(11)ų. Both carboxylic acids form the usual H-bonded dimers across crystallographic centers of inversion. The nitro groups are essentially in the ring planes, and the interplanar angle between the mean planes described by the atoms of the benzoyl substituents and those of the benzoic acid aryl rings are 69(1)° and 84(1)°, respectively. The lower cell volume, higher density, and lower solubility in ethyl ethanoate correlates with the greater packing efficiency in 5-nitro-2-benzoylbenzoic acid.