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Phenol, also known under the old name carbolic acid, is a colorless crystalline solid with a typical sweet tarry odor. Its chemical formula is C6H5OH and its structure is that of a hydroxyl group (-OH) bonded to a phenyl ring; it is thus an aromatic compound.
The word phenol is also used to refer in general to an aromatic compound in which a hydroxyl group (-OH) is bonded directly to a six-membered aromatic ring. In effect, phenols are a class of organic compounds of which the phenol discussed in this article is the simplest member. For more information on this class, see Phenols.
Phenol has a limited solubility in water (8.3 g/100 ml). It is slightly acidic: the phenol molecule has weak tendencies to lose the H+ ion from the hydroxyl group, resulting in the highly water soluble phenolate anion C6H5O−.
Phenol can be made from the partial oxidation of benzene, by the cumene process, or by the Raschig process. It can also be found as a product of coal oxidation.
Phenol has antiseptic properties, and was used by Sir Joseph Lister in his pioneering technique of antiseptic surgery, though the skin irritation caused by continual exposure to phenol eventually led to the substitution of aseptic (germ-free) techniques in surgery. It is one of the main components of the commercial antiseptic TCP.
It is also used in the production of drugs (it is the starting material in the industrial production of aspirin), weedkillers, and synthetic resins (Bakelite, one of the first synthetic resins to be manufactured, is a polymer of phenol with formaldehyde). Exposure of the skin to concentrated phenol solutions causes chemical burns; in laboratories where it is used, it is usually recommended that polyethylene glycol solution is kept available for washing off splashes. Notwithstanding the effects of concentrated solutions, it is also used in cosmetic surgery as an exfoliant, to remove layers of dead skin.
Dr. John H. Kellogg, the brother of Will Keith Kellogg who founded the Kellogg Company, advocated the application of "pure carbolic acid (phenol) on the clitoris of females to prevent masturbation in children".
Many prisoners in the Auschwitz I concentration camp hospital were killed by phenol injections.
Compared to aliphatic alcohols, phenol shows higher acidity. This is due to the mesomeric effect:
- Mesomeric structures of phenol, resulting in a partial positive charge δ+ on the oxygen atom. This together with the mesomeric stabilization of the phenolate anion causes an enhanced acidity.
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