Phenols are compounds having a hydroxyl group attached to an aromatic ring such as a benzene or naphthalene ring. They are used as intermediates in the production of a variety of valuable industrial products such as pharmaceuticals (e.g., aspirin) , explosives, picric acid, azo dyes, antioxidants, plastics, and disinfectants. Several phenols also possess one or more chlorine substituents attached to the aromatic ring have significant commercial importance. Chlorinated phenols and in particular 4-chloro isomers are useful intermediates in organic syntheses or as end products themselves. They are produced on an industrial scale and used in the production of antiseptics, herbicides, pesticides, and dyes.