(A) Pyridine (azine), and (B) pyridoxine, one of three naturally-occurring forms of vitamin B6.
Pyridine, C5H5N, is a colorless heterocyclic aromatic base with an unpleasant smell, found in bone oil and coal tar. It is produced from acetaldehyde (ethanal) and ammonia. Pyridine is used as a solvent and to denature grain alcohol (ethanol). Important derivatives are pyridoxine and niacin (see vitamin B complex).