Quinoline-4-carboxylic acid.

The title acid, C10H7NO2, crystallized in the centrosymmetric space group P2(1)/c with one molecule in the asymmetric unit. There is a single hydrogen bond. O-H...N, with a donor-acceptor distance of 2.596 (1) A. The carboxylic H atom is ordered. The dihedral angle between the best-fit quinoline core plane and the carboxyl plane is 45.9 (1) degrees. Structural comparisons are made with the closely related molecule 2-phenylquinoline-4-carboxylic acid.