L. I. Mazaletskaya

Kinetic parameters of the reaction of isobornylphenols with peroxy radicals

The stoichiometric factors of inhibition and the rate constants (k7) were measured for the reaction of isobornylphenols with peroxy radicals of ethylbenzene. The values of k7 of the compounds under study increase with an increase in the amount of alkyl substituents and OH groups on the aromatic ring. The introduction of the oxygen atom between the o-isobornyl substituent and the aromatic ring decreases k7 by a factor of 6.5. The inhibiting action of binary mixtures of sterically hindered phenols with 2-isobornyl-4-methylphenol and 2,6-diisobornyl-4-methylphenol in the initiated oxidation of ethylbenzene is close to additive.

Lecithin influence on the effectiveness of the antioxidant effect of flavonoids and α-tocopherol

Influence of the widely used food additive lecithin on the effectiveness of the inhibiting effect of the natural antioxidants (quercetin, dihydroquercetin, and α-tocopherol) has been studied in dependence on the rate of free radicals generation in the model oxidation reactions. It has been found that during the initiated and autoxidation of methyl oleat, lecithin decreased the antioxidant effectiveness of flavonoids. The effect value increased with the lecithin concentration increase. Under similar conditions while oxidation inhibiting by α-tocopherol and lecithin mixtures, the latter did not influence the tocopherol antioxidant effectiveness (additivity) or led to the increase of the inhibition effectiveness (synergism).

Inhibiting activity of isocamphyl substituted phenols and their mixtures with 2,6-di- tert -butylphenol in the initiated oxidation of ethylbenzene

The stoichiometric coefficients of inhibition and rate constants for the reaction of several terpenephenols (isocamphyl substituted phenols) with ethylbenzene peroxy radicals were measured. Their reactivity was found to increase as the number of alkyl substituents grew and decreased with an o-alkoxyl compared with o-alkyl substituent because of the formation of an intramolecular H-bond. In spite of similar antiradical activities of terpenephenols with isocamphyl and isobornyl substituents, the reactivities of phenoxyl radicals formed from them in the interaction with sterically hindered phenol molecules are substantially different. They are higher for isocamphylphenols with substituents turned with respect to the aromatic ring plane.

Synthesis and properties of new functional derivatives of 2-isobornyl-6-methylphenol

New functional derivatives containing an allyl, hydroxypropyl, or halopropyl group have been synthesized from 2-isobornyl-6-methylphenol and evaluated for antioxidant activity in the model ethylbenzene oxidation reaction.

Kinetic characteristics and physicochemical properties of isobornyl phenols with different alkyl substituents in the ortho -position

The rate constants were measured for the reactions of isobornyl phenols (IBPs) containing methyl and tert-butyl substituents in the ortho-position with peroxide radicals in the initiated oxidation of ethylbenzene. The IR spectra of IBPs were analyzed, and the influence of IBPs on phosphatidylcholine aggregation in hexane was studied. The influence of the structure of substituents on the kinetic characteristics and physicochemical properties of the studied phenols is ambiguous. The data obtained indicate the competitive influence of the donor ability and shielding effects of the alkyl substituent in the ortho-position to the hydroxy group on the kinetic characteristics and physicochemical properties of IBPs.

Tertiary aminomethylphenols and methylene bisphenols with isobornyl substituents in the reaction with diphenylpicrylhydrazyl and peroxy radicals in ethylbenzene

The effect of the structure of aminomethylphenols and methylene bisphenols with isobornyl substituents on their reactivity in interactions with peroxy radicals in ethylbenzene and with 1,1-diphenyl-2-picrylhydrazyl (DPPH) is studied. Isobornylphenols with o-aminomethyl substituents, as opposed to p-aminomethyl derivatives, were found to possess rather low activity in the initiated oxidation of ethylbenzene, due to the formation of intramolecular hydrogen bonds between the hydrogen atom of the OH group and the nitrogen atom of the aminomethyl substituent. An increase in activity of o-aminomethyl-substituted phenols with increasing polarity of the medium is observed in the reaction with DPPH. The reaction rate constants for the interaction between two isomeric 2,2′- and 4,4′-methylene-bisphenols having isobornyl moieties and ethylbenzene peroxy radicals are measured. The ratio between activities of the first and second OH groups in 2,2-methylene-bisphenol is shown to be close to 50.

Synthesis and antiradical activity of hybrid antioxidants based on isobornylphenols

Alkylation of isobornylphenols with allylbenzene in the presence of homogeneous and heterogeneous catalysts of different nature has been studied. The maximum yield of phenols containing isobornyl and 1-phenylpropyl moieties has been achieved in the presence of catalyst FIBAN K-1 at 100°С and catalyst concentration of 10%. The inhibiting action of isobornylphenol derivatives has been studied in the model reaction of ethylbenzene oxidation. Hybrid antioxidants on the basis of isobornylphenols were found to actively interact with peroxide radicals and, therefore, they can be considered as promising additives for conservation of quality and increase in service life of different organic compounds and materials.

Synthesis and properties of ω-(hydroxyaryl)alkylsulfides based on 2-isobornyl-6-methyl-4-propylphenol

Proceeding from 2-isobornyl-6-methyl-4-propylphenol new derivatives have been synthesized having sulfur atoms included in different functional groups. Antiradical and antioxidant activity, as well as membrane-protecting properties of the derivatives of 2-isobornyl-6-methyl-4-propylphenol in chemical and biological model systems have been investigated.

Effect of lecithin on the inhibitory efficiency of α-tocopherol during methyl oleate oxidation

It has been established that the effect of lecithin on the oxidation of methyl oleate depends on the rate of the free radical initiation: lecithin does not affect the reaction rate at high rates of radical initiation (the initiated oxidation) and accelerates the oxidation at low rates (autooxidation), causing the reduction of the induction period. The inhibitory action of mixtures of lecithin and the natural antioxidant α-tocopherol depends on the concentrations of both α-tocopherol and lecithin at different rates of oxidation. The inhibitory efficiency of mixtures with low concentrations of α-tocopherol is close to additive. Increasing the initial concentration of α-tocopherol in mixtures causes a gain in the synergistic effect. The synergistic effect depends extremally on lecithin concentration at high concentrations of α-tocopherol. The mechanism of the synergistic effect for the mixtures of α-tocopherol and lecithin is discussed.

Role of the nitrogen-containing moiety of phosphatidylcholines in the mechanism of inhibiting action of their mixtures with natural and synthetic antioxidants

The effect of a decrease in the inhibiting action of antioxidants (InH) was found in the model oxidation reaction of methyl oleate in the presence of phospholipids (egg phosphatidylcholine and dipalmitoylphosphatidylcholine), which increased with growing the oxidation extent of the substrate and initial concentrations of components of the mixture. It was shown that the decrease in the inhibition efficiency is due to the interaction of InH with the nitrogen-containing moiety of phospholipids, as demonstrated by spectrophotometric data and by similarity in the features of retardation of ethylbenzene oxidation by InH mixtures with phospholipids and N,N,N′,N′-tetramethylethylenediamine.