Effect of the conditions of liquid-phase oxidation of unsaturated compounds on the behavior of hydroquinoline antioxidants

The inhibition activity of hydroxy-and alkoxysubstituted 2,2,4-trimethyl-1,2,3,4-tetrahydroquinolines (HQs) was studied in R(+) limonene autooxidation and oxidation catalyzed by cationic surfactants and transition metal compounds. It was shown that HQs exhibit a high antioxidant activity in limonene autooxidation. In oxidation catalyzed by cationic surfactants and Fe(III), Co(II), or Mn(II) acetylacetonates, HQs also show a relatively high antioxidant activity and, additionally, react with hydroperoxides along with the reactions with peroxyl radicals in the presence of these catalysts. In the presence of Cu(II) compounds, HQs significantly accelerate the oxidation. It was found that HQs form complexes with Cu(II), which catalyze hydroperoxide degradation into free radicals.