Phenol, also known as carbolic acid and phenic acid, is an organic compound with the formula C6H5OH. It is a white crystalline solid at room temperature that solidifies at 41°C (106°F). The molecule consists of aphenyl (-C6H5) group, bonded to a hydroxyl (-OH) group. It is produced on a large scale (about 7 billion kg/year). It is used as a precursor to many materials and useful compounds. The chemical is only mildly acidic but requires careful handling due to its propensity to cause burns.
Phenol was first extracted from coal tar, and its major uses involve its conversion to plastics or related materials. Phenol is appreciably soluble in water, with about 8.3 g dissolving in 100 ml (0.88M). The sodium salt of phenol, sodium phenoxide, is far more water soluble.
Phenol is slightly acidic; the phenol molecules have weak tendencies to lose the H+ ion from the hydroxyl group, resulting in the highly water-soluble phenolate anion C6H5O– (also called phenoxide). Compared toaliphatic alcohols, phenol is about 1 million times more acidic, although it is considered a weak acid. It reacts completely with aqueous NaOH to lose the H+ ion, whereas most alcohols react only partially.Phenols are less acidic than carboxylic acids, and even carbonic acid.
Phenol is highly reactive toward electrophilic aromatic substitution as the oxygen atom’s pi electrons donate electron density into the ring. By this general approach, many groups can be appended to the ring via halogenation, acylation, sulfonation, and other processes. However, phenol’s ring is so strongly activated – second only to aniline – that bromination or chlorination of phenol leads to substitution on all carbons ortho and para to the hydroxy group, not only on one carbon.
TCC’s phenol plays an unseen, but major role in our everyday lives. Plywood, window glazing, DVDs and CDs, computers, sports equipment, automotive parts and accessories, and flat panel televisions are some of the many items that rely on this important raw material.
Phenol is a major component of the phenolic adhesives used in wood products such as plywood and oriented strand board. It is also used to produce phenolic resins, which are used in the molding of heat-resistant components for household appliances, counter-tops and flooring laminates, and foundry castings. In addition, it is a valuable intermediate in the manufacture of detergents, agricultural chemicals, medicines, plasticizers, and dyes.
The largest single market for phenol is in the production of Bisphenol A (BPA), which is manufactured from phenol and acetone. BPA is used to manufacture polycarbonate (the largest and fastest growing use for BPA) and epoxy resins. Both polycarbonate and epoxy resins are used in many different industries and in countless items which we encounter every day like CDs, flat panel televisions, circuit boards and fiberglass boats.
When reacted with bromine, BPA forms the fire retardant tetrabromobisphenol A. BPA is also used to manufacture engineering thermoplastics such as polysulfones and polyarylates.
Phenol is so inexpensive that it attracts many small-scale uses. It once was widely used as an antiseptic, especially as Carbolic soap, from the early 1900s through the 1970s. It is a component of industrial paint strippers used in the aviation industry for the removal of epoxy, polyurethane and other chemically resistant coatings.
Phenol derivatives are also used in the preparation of cosmetics including sunscreens, hair dyes, and skin lightening preparations.