Strong intramolecular O-H center dot center dot center dot O hydrogen bonds in quinaldic acid N-oxide and picolinic acid N-oxide

The title compounds contain very short intramolecular hydrogen bonds of the type C-O-H ... O-N. The O ... O distances are 2.425 (2) Angstrom in picolinic acid N-oxide (2-carboxypyridine N-oxide), C6H5NO3, (I), and 2.435 (2) Angstrom in quinaldic acid N-oxide (2-carboxyquinoline N-oxide), C10H7NO3, (II). In (II), this is associated with slight molecular distortion from planarity, while in (I), such an effect cannot be observed because the molecule crystallizes on a mirror plane.