4,4'-Biphenol Explained

4,4′-Biphenol is an aromatic organic compound, and one of three symmetrical isomers of biphenol. It is a colourless crystalline solid with a high melting point. It is primarily used in the production of polymers, particularly liquid crystals where it imparts high thermal stability.

Synthesis

The industrial synthesis of 4,4′-biphenol was developed by Allan Hay in the 1960s.^{[1] [2]} As the direct oxidative coupling of phenol gives a mixture of isomers,^{[3] [4]} 4,4′-biphenol is instead prepared from 2,6-di-tert-butylphenol, where para-coupling is the only possibility. The reaction with oxygen produces phenol-radicals which undergo rapid dimerisation, forming a diphenoquinone. This is reduced to the tetra-butyl-biphenyl derivative by a reaction with additional 2,6-di-tert-butylphenol, in an oxygen-free environment. In the final step, high temperature dealkylation 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) can be produced.^[5]

Safety

4,4'-Biphenol had actually been elucidated to have an estrogenic SAR.^[6]

See also

• 2,2'-Biphenol
• Bisphenol

Notes and References

1. Hay . A.S. . Dehydrogenation reactions with diphenoquinones . Tetrahedron Letters . January 1965 . 6 . 47 . 4241–4243 . 10.1016/S0040-4039(01)89114-0.
2. Hay . Allan S. . p,p'-Biphenols . The Journal of Organic Chemistry . April 1969 . 34 . 4 . 1160–1161 . 10.1021/jo01256a098.
3. Encyclopedia: Helmut Fiege . Heinz-Werner Voges . Toshikazu Hamamoto . Sumio Umemura . Tadao Iwata . Hisaya Miki . Yasuhiro Fujita . Hans-Josef Buysch . Dorothea Garbe . Wilfried Paulus . 3 . Phenol Derivatives. Ullmann's Encyclopedia of Industrial Chemistry. 2002. Wiley-VCH. Weinheim. 10.1002/14356007.a19_313. 3527306730 .
4. Encyclopedia: M. K.. O’Brien. B.. Vanasse . Vanadium(IV) Chloride. Encyclopedia of Reagents for Organic Synthesis . L. . Paquette . 2004 . J. Wiley & Sons . New York, NY. 10.1002/047084289X.rv001. 0471936235.
5. Hay . Allan S. . Polymerization by oxidative coupling. II. Oxidation of 2,6‐disubstituted phenols . Journal of Polymer Science . April 1962 . 58 . 166 . 581–591 . 10.1002/pol.1962.1205816634.
6. Dodds. E. C.. Lawson. W.. A Simple Aromatic oestrogenic Agent with an Activity of the Same Order as that of estrone. Nature. 139. 3519. 1937. 627–628. 0028-0836. 10.1038/139627b0. 4119670 .