Aniline is the simplest aromatic amine, characterized by an amino group attached to a phenyl ring. Aniline is an industrially significant commodity chemical, as well as a versatile starting material for fine chemical synthesis, with its main use being in the manufacture of precursors to polyurethane, dyes, and other industrial chemicals; like most volatile amines, it has a distinctive and unpleasant odor of rotten fish, it ignites readily, burning with a smoky flame characteristic of aromatic compounds. Aniline is toxic to humans upon exposure.