Kinetics of the radical-chain oxidation of methyl oleate inhibited by 5-amino-6-methyluracil and 5-amino-1,3,6-trimethyluracil

Kinetics and Catalysis - The effects of 5-amino-6-methyluracil (AMU) and 5-amino-1,3,6-trimethyluracil (ATMU) on the rate of oxygen uptake in methyl oleate (MO) radical-chain oxidation initiated by...     

Antiradical activity of aryl- and hetarylhydrazones in ethylbenzene oxidation

A relation between the kinetic parameters of the antiradical activity of aryl and hetarylhydrazones and their electronic structure is revealed in the form of the correlation between the reaction rate constants, bond energies of the reaction centers and the antioxidants ionization potentials. The relations obtained can be used to predict the antiradical activity in a series of hydrazones.     

Protonation of 5-aminouracil, 5-amino-1,3,6-trimethyluracil,and 6-aminouracil in aqueous solutions

The processes of protonation of 5-aminouracil, 5-amino-1,3,6-trimethyluracil, and 6-aminouracil in aqueous solutions were studied by UV and ¹³С NMR spectroscopy in combination with quantum-chemical calculations.     

On the mechanism of deiodination of 5-iodo-1,3,6-trimethyluracil

Russian Chemical Bulletin - Dehalogenation of 5-iodo-1,3,6-trimethyluracil in acidic medium in the presence of either KCl or KBr as the nucleophile sources proceeded as the halophilic reaction to...     

Acid-Base Properties of 5-Hydroxy-1,3,6-trimethyluracil in Aqueous Solutions

Russian Journal of General Chemistry - 5-Hydroxy-1,3,6-trimethyluracil has been studied using 1H, 13C, and 15N NMR as well as UV spectroscopy. The constants and thermodynamic characteristics of its...     

Antiradical activity of the hormonal preparation estrone in lipid models undergoing oxidation

The rate constants and stoichiometric coefficients of chain termination in the oxidation of lipid models (methyl esters of acids of the oleic series: cis-6-, cis-9-, trans-9-, and trans-11-C₁₇H₃₃COOCH₃) by the main representative of the follicular hormones — estrone (313–348 K) — and for comparison by the phenol 2,6-ditert-butyl-4-methylphenol (323.15 K) were measured. The strength of the OH bond in the estrone molecule was estimated.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 29, No. 5, pp. 445–448, September–October, 1993.     

Synthesis of the 5-selena-1,3,6-triazacycl[3.2.3]azine system

The syntheses and properties of four phenyl derivatives of the 5-selena-1,3,6-triazacycl[3.2.3]azine system are described. Bromination of 4-phenyl-5-selena-1,3,6-triazacycl[3.2.3]azine, is found to occur in position 8.     

Mathematical modeling of the inhibited radical chain oxidation of organic compounds

A new software package is suggested for solving the inverse kinetic problem for inhibited oxidation reactions of organic compounds. The software has been developed using inhibited n-decane oxidation as the model reaction.     

Increasing the ketone selectivity of the cobalt-catalyzed radical chain oxidation of cyclohexane

A variety of heterogeneous catalysts for the radical chain oxidation of cyclohexane has been prepared by immobilization of the well-defined cobalt acetate oligomers [py(3)Co(3)(mu(3)-O)(OH)(O(2)CCH(3))(5)](PF(6)) (1) and [py(4)Co(2)(OH)(2)(O(2)CCH(3))(3)](PF(6)) (2) on carboxy-modified mesoporous silica supports A-D by carboxylate exchange. The catalytic oxidation of cyclohexane with tert-butyl hydroperoxide (TBHP) in the presence of these homogeneous and immobilized cobalt acetate complexes afforded the corresponding alcohol and ketone in high yield. The immobilization of 1 and 2 results in a significant increase of catalytic activity. TBHP acts as a radical initiator and as source of molecular oxygen, which is also involved in the overall oxidation process. The rate of cyclohexane conversion is limited by the diffusion of molecular oxygen, and steady-state concentrations of cyclohexanone (K, ketone) and cyclohexanol (A, alcohol) are established; these determine the maximum K:A ratio.     

Investigation of antiradical activity of pyrazolo-[3,4-b]pyranes in ethylbenzene oxidation

Kinetic parameters of the antiradical activity of pyrazolo [3,4-b]pyranes in the initiated low-temperature oxidation of ethylbenzene determined by the chemiluminescence method indicate that these pyranes have considerable antiradical properties like the known effective inhibitors.

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[3,4-b] qp . , [3,4-b] .

     

Mechanism of 5-amino-6-methyluracil-inhibited oxidation of organic compounds

Based on experimental and theoretical data obtained in the mechanism study of the 5-amino-6-methyluracil-inhibited radical chain oxidation of 1,4-dioxane, a scheme for the process is proposed. A kinetic analysis of the scheme has been performed to obtain an equation describing the regularities of oxygen consumption that agree with the experimental data and provide evidence in favor of the chain consumption of the inhibitor under certain conditions. The composition of resulting products confirms the proposed mechanism.     

Antioxidant effect of tocopherolhydroquinone on the oxidation of ethylbenzene

The antioxidation properties of tocopherolhydroquinone were studied by the chemiluminescence method in combination with mathematical simulation. The rate constant of the liquid-phase reaction of tocopherolhydroquinone with the α-ethylphenylperoxy radical was determined (2.4 × 10⁶ l mol^?1 s^?1). The rate constants of chain propagation in the reactions of the tocopherolhydroquinone radical with RH (≤0.07 l mol^?1 s^?1) and O₂ (950 l mol^?1 s^?1) were estimated.     

Long-lived radical cations as model compounds for the reactive one-electron oxidation product of vitamin E

Heterocyclic compounds with structures similar to vitamin E, but without the hydroxyl hydrogen atom, were synthesized and their electrochemical behavior examined in acetonitrile solutions and as solids in aqueous solutions of varying pH by attaching the compounds to the surface of a glassy carbon electrode. Compound 1, containing a fully methylated aromatic ring was found to be the most long-lived following one-electron oxidation, with its radical cation (1+*) surviving in acidic aqueous solutions and able to be isolated as a salt, 1+*(SbF6-), when reacted with NOSbF6 in CH3CN. Electrochemical, UV-vis and FTIR experiments on 1+*, in addition to the results from theoretical calculations, indicated that the electrochemical, electronic and structural properties of 1+* are very similar to those of the radical cation of vitamin E.     

Hydroxyl radical reactions with 2-chlorophenol as a model for oxidation in supercritical water

To determine the detailed mechanism of 2-chlorophenol (2-CP) oxidation in supercritical water, both the experiments and theoretical calculations were conducted in this paper. A set of experiments was performed to oxidize 2-CP in supercritical water under temperatures of 380–420 °C, pressure of 25 MPa, residence times of 0–60 s, and H₂O₂ as oxidant. By determining the molar yields of products, the primary single-ring products were identified as chlorohydroquinone, 2,4-dichlorophenol (2,4-DCP), 2,6-DCP, and 4-CP. The trends for the molar yields of the four products were analyzed at various temperatures and residence times. And built upon the trends, the possible reaction pathways were conjectured. Subsequently, the reaction mechanism was further verified by theoretical calculations, in which density functional theory was adopted as the computational method. The calculated results have well illustrated the experimental results and ascertained the reaction paths we proposed.