This article discusses the oxidation of methyl linoleate in micelles, initiated by the lipid-soluble initiator 2,2'-azobis (2,4-dimethylvaleronitrile) (AMVN). It was shown that the rate constant (k(i)) is initiated in micelles for AMVN significantly lower than the known rate constant of initiation in true solutions. This can be explained by the reduced probability of AMVN radicals leaving the cage and an increase in the rate of chain termination between initiator radicals under conditions of low oxygen content. This conclusion was confirmed by quantum chemical calculations. Surprisingly, when determining the AMVN initiation rate constant for the consumption of nitroxyl radicals (>NO center dot), the ki depends on the concentration >NO center dot, this is due to the dependence of the probability of the nitroxyl radical and initiator radicals in micelles meeting on their concentration. Upon initiation of AMVN, no hydroperoxyl radical is expelled.

Using the model of methyl linoleate (LH) oxidation in micelles, the effect of cysteine on the antioxidant activity of nitroxyl radicals (NR) in micelles is studied. It is found that cysteine enhances the antioxidant effect of NR with a low reduction potential of the oxoammonium cation + nitroxyl radical pair, which is due to the formation of the corresponding hydroxylamines (HA).

Kinetics of the reduction of nitroxides with cysteine in the presence of a source of superoxide radicals was studied. The reactivity of nitroxides in this process is determined by the reduction potential of the N-oxoammonium cation / nitroxide pair. The rate-limiting step of the reaction is the nitroxide oxidation by the hydroperoxyl radical to the N-oxoammonium cation.

The kinetics of the oxidation of methyl linoleate in micelles inhibited by stable nitroxides under the conditions of initiation by superoxide radicals was studied. Multiple breakdown of the oxidation chains was observed in this process. The antioxidant activity of nitroxides increased when the reduction potential of the oxoammonium cation/nitroxide pair decreased and their lipophilicity increased.

The kinetics of oxidation of methyl linoleate in micelles inhibited by stable nitroxyl radicals in the presence of superoxide dismutase was studied. In the presence of superoxide dismutase, nitroxyl radicals decrease the rate of oxidation to a lower extent and the process is characterized by lower inhibition coefficients. The results obtained demonstrate an important role of hydroperoxide radical in the mechanism of nitroxyl radical regeneration during the oxidation of methyl linoleate in micelles.

The kinetics of methyl linoleate oxidation in micelles inhibited by five-membered cyclic nitroxyl radicals and the corresponding hydroxylamines was studied. The partial regeneration of nitroxyl radicals in this process was found. The activity of the studied inhibitors increases with an increase in their lipophilicity.

The kinetics of methyl linoleate oxidation in micelles inhibited by nitroxyl radicals and hydroxylamines was studied. The regeneration of nitroxyl radicals in this process was found. The activity of the studied inhibitors increases with increasing their lipophilicity. This effect was explained by increasing the distribution coefficient of the antioxidants in a micelles–water system. The reaction of nitroxyl radicals with the hydroperoxide radical formed upon the oxidation of methyl linoleate in micelles is proposed to be the key reaction in nitroxyl radical regeneration.

Kinetics and equilibrium of the acid‐catalyzed disproportionation of cyclic nitroxyl radicals R2NO• to oxoammonium cations R2NO+ and hydroxylamines R2NOH is defined by redox and acid–base properties of these compounds. In a recent work (J. Phys. Org. Chem. 2014, 27, 114‐120), we showed that the kinetic stability of R2NO• in acidic media depends on the basicity of the nitroxyl group. Here, we examined the kinetics of the reverse comproportionation reaction of R2NO+ and R2NOH to R2NO• and found that increasing in –I‐effects of substituents greatly reduces the overall equilibrium constant of the reaction K4. This occurs because of both the increase of acidity constants of hydroxyammonium cations K3H+ and the difference between the reduction potentials of oxoammonium cations ER2NO+/R2NO• and nitroxyl radicals ER2NO•/R2NOH. pH dependences of reduction potentials of nitroxyl radicals to hydroxylamines E1/3Σ and bond dissociation energies D(O–H) for hydroxylamines R2NOH in water were determined. For a wide variety of piperidine‐ and pyrrolidine‐1‐oxyls values of pK3H+ and ER2NO+/R2NO• correlate with each other, as well as with the equilibrium constants K4 and the inductive substituent constants σI. The correlations obtained allow prediction of the acid–base and redox characteristics of redox triads R2NO•–R2NO+–R2NOH. Copyright © 2014 John Wiley & Sons, Ltd.

AcidaEurocatalyzed disproportionation of cyclic nitroxyl radicals R2NOaEuroC includes the halfaEuroreactions of their oxidation to oxoammonium cations R2NO+ and reduction to hydroxylamines R2NOH. For many nitroxyl radicals, this reaction is characterized by itsaEuro?100% reversibility. Quantitative characteristics of acidaEuro'base and redox properties of the whole redox triad may be obtained from research of kinetics and equilibrium of this reaction. Here, we have examined the kinetics for the disproportionation of twenty piperidineaEuro, pyrrolineaEuro, pyrrolidineaEuro, and imidazoline nitroxyl radicals in aqueous H2SO4, and interpreted it in terms of the excess acidity function X. The rateaEurolimiting step of this reaction is R2NOaEuroC oxidation by its protonated counterpart R2NOH+aEuroC. Kinetic stability of R2NOaEuroC in acidic media depends on the basicity of nitroxyl group. This basicity is influenced predominantly by protonation of another, more basic group in radical structure, and its proximity to nitroxyl group. The discovered estimates of pK values for radical cations R2NOH+aEuroC (from a?'5.8 to a?'12.0) indicate a very low basicity of nitroxyl groups in all commonly used R2NOaEuroC. For the first time, a linear correlation is obtained between the oneaEuroelectron reduction potentials of oxoammonium cations and the basicity of nitroxyl groups of related radicals. Copyright a (c) 2013 John Wiley & Sons, Ltd.

Heat treatment of polydimethylvinylethynylcarbinol and its methyl ether, having an acetylene bond in each monomer unit, is accompanied by polycyclization through acetylene bonds to form ladder polyenes, which possess paramagnetism.

Dichlorocarbene selectively adds to the double bond of the methyl ether of dimethylvinylethynylcarbinol.

AbstractBeim Kochen des Methyläthers von Dimethyläthinylvinyl‐carbinol (I) mit TrichloF acetat in Dimethoxyäthan wird das entstehende Dichlorcarben (II) unter Bildung des Methyläthers (III) addiert.