PHENOL

any of a family of organic compounds characterized by a hydroxyl (-OH) group attached to a carbon atom that is part of an aromatic ring. Besides serving as the generic name for the entire family, the term phenol is also the specific name for its simplest member, monohydroxybenzene (C6H5OH), also known as benzenol, or carbolic acid. Phenols are similar to alcohols but form stronger hydrogen bonds. Thus, they are more soluble in water than are alcohols and have higher boiling points. Phenols occur either as colourless liquids or white solids at room temperature. Many phenols have a sharp, spicy odour, but phenol smells bland and sweetish. It is, however, highly toxic and caustic. So-called natural phenol can be made from the distillation of coal tar or crude petroleum. Other phenols of natural origin are found in essential oils, which are derived from seeds or leaves of plants. Most synthetic phenol is produced by either the hydrolysis of chlorobenzene or the oxidation of isopropylbenzene, methods that use benzene as a starting material. More general syntheses, such as diazotization of arylamines, are used for more complex phenols. Phenols are acidic and react with strong bases to form alkali-metal salts known as phenoxides. The most important reaction of phenol is its condensation (which produces water as a side effect) with formaldehyde. This forms synthetic polymers, called phenol-formaldehyde (phenolic) resins, that are widely used plastics. Members of the phenol series with higher molecular weight, and derivatives of phenol, have supplanted the latter as an industrial antiseptic (e.g., for germicidal cleaning). Alkylphenols are used in synthetic detergents and to produce oxygen inhibitors.