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Peroxy radicals formed by the autoxidation of styrene react with 4-tert-butylcatechol (TBC) to give a tert-butylsemiquinone radical. When the TBC radical is generated in the presence of a 2,6-di-tert-butyl-7-substituted quinone methide (QM), the result is o-TBC addition at the 7-position of the QM. The effects of TBC/QM addition are observed during styrene polymerization retarder testing under aerobic conditions for 2-(3,5-di-tert-butyl-4-oxocyclohexa-2,5-dien-1-ylidene)acetonitrile (QM-CN), 2,6-di-tertbutyl-4-(methoxymethylene)cyclohexa-2,5-dienone (QM-OMe), and 4-benzylidene-2,6-di-tert-butylcyclohexa-2,5-dienone (QM-Ph). Increasing the concentrations of QM-Ph and TBC during aerobic batch styrene polymerization allowed for silica gel chromatography isolation of 5-(tert-butyl)-3-((3,5-di-tert-butyl-4-hydroxyphenyl)(phenyl)methyl)benzene-1,2-diol, a novel compound. Radicals generated by the autoxidation of cumene and by homolysis of dicumylperoxide also activate TBC/QM addition. TBC/QM interaction causes a reduction in the performance of QMs as styrene polymerization retarders under aerobic conditions. Under anaerobic test conditions, a better simulation of industrial styrene purification, the TBC/QM interaction leads to only minimal reduction in retarder performance.

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