Correlation between the structure and inhibiting activity of phenosan derivatives

Sterically hindered phenolic antioxidants (AOs) of the IKhFAN family are characterized as inhibitors of initiated oxidation of methyl oleate in homogeneous chlorobenzene solutions and in aqueous emulsions in the presence of dodecyl sulfate. The IKhFANs inhibit oxidation by scavenging peroxo radicals and by decomposing hydroperoxides to yield molecular products. The effect of an IKhFAN is governed by its chemical structure and by oxidation conditions. The IKhFANs slow down methyl oleate oxidation in lipid solution more effectively than comparable concentrations of -tocopherol, dibunol, phenosan K, or phenosan ester. The most effective is IKhFAN-10, in which the R³ radical is the shortest (CH₃). The inhibiting effect of the AOs weakens markedly with increasing chain length of R³. The specific features of the observed oxidation kinetics are explained by the formation of microheterogeneous systems involving AOs. In these systems, the phenolic OH groups are directed to the micelle center and, as a consequence, can hardly react with RO₂^· radicals. In the IKhFAN group in which R³ ranges from C₈H₁₇ to C₁₆H₃₃, the induction period grows in proportion to the number of carbon atoms. In an aqueous emulsion, the overall inhibiting effects of structurally different IKhFANs are similar and weaker than effects in homogeneous solution.Translated from Kinetika i Kataliz, Vol. 45, No. 6, 2004, pp. 863–871Original Russian Text Copyright © 2004 by Storozhok, Perevozkina, Nikiforov, Rusina, Burlakov.