4,4′-Biphenol is an

organic compound Some chemical authorities define an organic compound as a chemical compound that contains a carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. For example, carbon-co ...

with the formula / It is one of three symmetrical isomers of

biphenol In organic chemistry, a biphenol refers to compounds with the formula (C6H4OH)2. Such compounds formally result from the coupling of two phenols. {{short description, Chemical compound Three symmetrical isomer In chemistry, isomers are mole ...

. It is a colourless crystalline solid with a high melting point. It is primarily used in the production of polymers, particularly

liquid crystal Liquid crystal (LC) is a state of matter whose properties are between those of conventional liquids and those of solid crystals. For example, a liquid crystal can flow like a liquid, but its molecules may be oriented in a common direction as i ...

s where it imparts high thermal stability, and PPSU-type

polysulfone Polysulfones are a family of high performance thermoplastics. These polymers are known for their toughness and stability at high temperatures. Technically used polysulfones contain an aryl- SO2-aryl subunit. Due to the high cost of raw material ...

(also called polyphenylenesulfone, or Radel R).

Synthesis

The industrial synthesis of 4,4′-biphenol was developed by

Allan Hay Allan Stuart Hay FRS (July 23, 1929 – August 14, 2017) was a Canadian chemist, and Tomlinson Emeritus Professor of Chemistry at McGill University. He is best known for his synthesization of Polyphenylene Oxide, leading to the development of No ...

in the 1960s. As the direct

oxidative coupling Oxidative coupling in chemistry is a coupling reaction of two molecular entities through an oxidative process. Usually oxidative couplings are catalysed by a transition metal complex like in classical cross-coupling reactions, although the under ...

of phenol gives a mixture of isomers, 4,4′-biphenol is instead prepared from

2,6-di-tert-butylphenol 2,6-Di-''tert''-butylphenol is an organic compound with the structural formula 2,6-((CH3)3C)2C6H3OH. This colorless solid alkylated phenol and its derivatives are used industrially as UV stabilizers and antioxidants for hydrocarbon-based produc ...

, where para-coupling is the only possibility. A reaction with oxygen produces phenol-radicals which undergo rapid dimerisation, ultimately forming a diphenoquinone. Syn44-biphenol

This intermediate is reduced to the tetra-butyl-biphenyl derivative by a reaction with two equivalents of 2,6-di-tert-butylphenol, in an oxygen-free environment (with the radicals generated dimerising to form additional tetra-butyl-biphenyl). In the final step, high temperature

dealkylation Alkylation is a chemical reaction that entails transfer of an alkyl group. The alkyl group may be transferred as an alkyl carbocation, a free radical, a carbanion, or a carbene (or their equivalents). Alkylating agents are reagents for effecting al ...

is performed to remove the butyl groups, producing the desired 4,4′-biphenol product. If groups less bulky that t-butyl are used then polyphenylene ethers such as

poly(p-phenylene oxide) Poly(''p''-phenylene oxide) (PPO), poly(''p''-phenylene ether) (PPE), poly(oxy-2,6-dimethyl-1,4-phenylene), often referred to simply as polyphenylene oxide, is a high-temperature thermoplastic with the general formula (C8H8O)n. It is rarely used ...

can be produced.

Safety

4,4'-Biphenol exhibits estrogenic SAR.

References

{{DEFAULTSORT:Biphenol, 4, 4'- 4-Hydroxyphenyl compounds Biphenyls

Synthesis

Safety

See also

References