4,4'-Biphenol

Synthesis

The industrial synthesis of 4,4′-biphenol was developed by Allan Hay in the 1960s. As the direct oxidative coupling of phenol gives a mixture of isomers, 4,4′-biphenol is instead prepared from 2,6-di-tert-butylphenol, where para-coupling is the only possibility. A reaction with oxygen produces phenol-radicals which undergo rapid dimerisation, ultimately forming a diphenoquinone.

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 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.

Safety

4,4'-Biphenol exhibits estrogenic SAR.

References

References

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7. (April 1962). "Polymerization by oxidative coupling. II. Oxidation of 2,6-disubstituted phenols". Journal of Polymer Science.
8. (1998). "Interaction of Estrogenic Chemicals and Phytoestrogens with Estrogen Receptor β". Endocrinology.