Redox properties of hydrogenated quinoline derivatives — inhibitors in oxidation processes of hydrocarbons

Half-wave potentials of the one-electron electrochemical oxidation (E _1/2 ^ox) of hydroquinolines with different degrees of heterocycle hydrogenization as well as containing substituents of various natures in the benzene ring and heterocycle have been measured. Linear correlations betweenE _1/2 ^ox and the values of the Hammett polar -constants form- andp-substituents in dihydroquinolines and related sulfur-containing dithiolthiones were established. The character of the variation ofE _1/2 ^ox in the series of hydroquinolines was found to correlate with the characteristic features of the inhibiting action of these compounds in the liquid-phase oxidation of various hydrocarbons. However, in contrast to phenolic antioxidants for hydroquinolines, there is no dependence of the retardation period onE _1/2 ^oxin the oxidation of hydrocarbons at temperatures higher than 100 °C.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 610–613, April, 1994.     

Temperature effect on the rate of formation of free radicals in CTAB-catalyzed decomposition of hydroperoxides

The temperature effect on the rate of the decomposition of hydroperoxides and the rate of the formation of free radicals in the oxidation of ethylbenzene with molecular oxygen in the presence of -phenylethyl hydroperoxide—cetyltrimethylammonium bromide (CTAB) as a catalytic system for free radical generation was studied by kinetic methods (from the oxygen consumption and hydroperoxide decomposition rates) and the inhibition method involving different acceptors of free radicals.     

Features of Methyl Linoleate Oxidation in Triton X-100 Micellar Buffer Solutions

Russian Journal of Applied Chemistry - The kinetics of oxygen absorption during the oxidation of methyl linoleate in Triton X-100 micelles has been studied. The order of the reaction with respect...     

Reactions of N,N′-diphenyl-p-quinonediimine with hydroquinone, α-tocopherol,and other antioxidants

Phenols (hydroquinone and -tocopherol) and heterocyclic aminophenols (2,2,4-trimethyl-6-ethoxy-1,2-dihyroquinoline) reduce N,N-diphenyl-p-quinonediimine (A) to the diamine. With difunctional hydrogen atom donors, the reaction rate is proportional to the concentrations of the reactants. The effective rate constants have been determined over a range of temperatures. In the reaction of A with -tocopherol, plots of rate versus initial concentrations are nonlinear, 2,6-Di-tert-butyl-4-methylphenol and 2,2,4-trimethyl-6-ethoxy-1,2-dihyroquinoline do not react with A under the same conditions.N.N. Semenov Institute of Chemical Physics, Russian Academy of Sciences, 117977 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 2, pp. 417–420, February, 1992.     

Specific features of lecithin oxidation in organic solvents

The effect of the structurization of a natural surfactant, egg phosphatidylcholine (lecithin, LH), in solutions in organic solvents on the kinetics of its oxidation by molecular oxygen is studied. The oxidation of LH proceeds via chain free-radical mechanism like the oxidation of hydrocarbons and oils; the oxidizability of LH is close to that of cyclohexene derivatives, methyl linoleate, and sunflower oil. The formation of reverse micelles in LH solutions results in a nonlinear dependence of the rate of oxygen absorption on the substrate concentration. Strong oil-soluble antioxidants decelerate oxygen absorption, however, do not suppress intramicellar oxidation. The addition of CaCl₂ causes the disintegration of reverse LH micelles. Resulting LH-CaCl₂ adduct is oxidized at a higher rate than the original LH and catalyzes the formation of radicals through the decomposition of hydroperoxides similarly to acetylcholine chloride.     

Micellar catalysis in the oxidation of lipids

The features of the catalytic effects of surfactants (S) in the oxidation of hydrocarbons and lipids are considered. It is shown that the primary amphiphilic products of the oxidation of hydroperoxides (ROOH) and lipids and the known cationic surfactants form mixed micelles {nS-mROOH} in which the accelerated decomposition of ROOH occurs and other polar components, such as metal-containing compounds, inhibitors, etc., can be concentrated, thus producing a large effect on the oxidation rate and mechanism.     

Effects of chain transfer and recombination/disproportionation of inhibitor radicals on inhibited oxidation of lipids

The kinetics of inhibited oxidation of lipids was studied by computer simulation to evaluate the contributions of the recombination/disproportionation of inhibitor radicals and chain transfer to retardation effects. The influence of inhibitor regeneration on the induction periods and inhibited oxidation rate was demonstrated. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1915–1920, October, 1999.     

Decomposition of cumene hydroperoxide in the systems of normal and reverse micelles formed by cationic surfactants

Decomposition of cumene hydroperoxide into free radicals in aqueous and organic media in the presence of cationic surfactants at 37°C is studied by the method of inhibitors using quercetin as an acceptor of radicals. It is found that cationic surfactants catalyze the decomposition of cumene hydroperoxide into radicals, the catalytic effect in an organic medium being higher than that in an aqueous solution. Catalytic action of surfactants greatly depends on the counterion nature. Cetyltrimethylammonium chloride has the highest catalytic activity. Characteristics of surface activity of some cationic surfactants and hydroperoxides are obtained.