Any of a class of organic compounds with a hydroxyl group (-OH; see functional group ) attached to a carbon atom in a ring of an aromatic compound .
The simplest one, carbolic acid (C 6 H 5 OH), is also called phenol; its most important reaction is with formaldehyde , with which it forms widely used polymers called phenol-formaldehyde (phenolic) resins. Phenols are similar to alcohol s but form stronger hydrogen bonds (see bonding ), so they dissolve more readily in water and boil at higher temperatures. They may be colourless liquids or white solids; many have a sharp, spicy odour. Some are found in essential oil s. Phenols with higher molecular weight s and phenol derivatives have supplanted phenol itself as industrial antiseptic s (germicidal cleaners). See also Leo Baekeland .