2-[N-(2,4-Difluoro­phen­yl)carbamo­yl]-3,4,5,6-tetra­fluoro­benzoic acid

The title compound, C(14)H(5)F(6)NO(3), was synthesized by condensation of tetra­fluoro­phthalic anhydride and 2,4-difluoro­aniline. It was then recrystallized from hexane to give a nonmerohedral twin with two crystallographically unique mol­ecules in the asymmetric unit. The refined twin fraction is 0.460 (3). Torsional differences between the aryl rings and the central amide group account for the presence of two unique mol­ecules. The compound packs as double tapes formed by O—H⋯O and N—H⋯O hydrogen-bonding inter­actions between each unique mol­ecule and its symmetry equivalents.