Influence of tungsten compounds on reaction of 1-octene epoxidation by tert-butyl hydroperoxide and hydroperoxide decomposition

Catalytic ability of tungsten compounds in the reaction of hydroperoxide epoxidation of 1- octene and tert-butyl hydroperoxide decomposition was investigated. It is shown that the nature of ligand has significant effect on the catalytic activity of tungsten compounds in these reactions. It is established that boride and silicide of tungsten are the best choice for epoxidation reaction, whereas tungsten carbide exhibits poor activity. Tungsten boride is also the most active in the hydroxide decomposition reaction.

Radical Scavenging Activity of Olive Oil Phenolic Antioxidants in Oil or Water Phase during the Oxidation of O/W Emulsions: An Oxidomics Approach

Omics approaches are recently being applied also in food lipid oxidation, to increase knowledge of oxidation and antioxidation mechanisms. The so-called oxidomics throws a wider spot of light on the complex patterns of reactions taking place in food lipids, especially in dispersed systems. This research aimed to investigate the radical scavenging activity of olive oil phenolic antioxidants (OPAs) in O/W emulsions, as affected by the phase in which they were added. This allowed one to assess whether different behaviors could be expected from antioxidants originally present in phenolic-rich olive oils compared to natural antioxidants added in the water phase during emulsion production. Hydroperoxide decomposition kinetics and the analysis of volatile pattern provided an outline of antioxidation mechanisms. Though being effective in slowing down oxidation when added both in the oil and water phase, OPAs interfered in different ways with oxidation pathways, based on the phase in which they were added. OPAs added to the water phase were more effective in slowing down hydroperoxide decomposition due to the hydrophilic radical initiator. On the other hand, OPAs present in the oil were more effective in preventing radical propagation, with relevant consequences on the volatile pattern.

Antioxidant properties of derivatives of 3,4-dihydropyrimidin-2-one with sterically hindered phenolic substituent in heterocycle

In the processes of free-radical oxidation of organic compounds, the inhibitory action of the inhibitor is mainly due to either the breakdown of the reaction chains on its molecules, or the slowdown of the decomposition of intermediate hydroperoxides, or both at the same time. We analysed the inhibitory properties of 4-[3,5-di(tert-butyl)-4-hydroxyphenyl]-5-ethoxycarbonyl-6-methyl-3,4-dihydropyrimidin-2-one (I) and 4-[4-methoxyphenyl]-5-ethoxycarbonyl-6-methyl-3,4-dihydropyrimidin-2-one (II) gasometry and hydroperoxide decomposition methods. These compounds were obtained by the three-component Biginelli reaction. The decomposition of cumene hydroperoxide in dimethylformamide under these conditions is described by a first-order kinetics equation. The first compound significantly inhibits the decomposition of hydroperoxide. The dependence of the effective rate constant of the decomposition of cumene hydroperoxide on the first concentration is described by the equation: . The second compound also slows the decomposition of hydroperoxide, but much less than the first compound. Therefore, both the phenolic moiety and the urea moiety of the dihydropyrimidinone cycle take part in slowing the cumene hydroperoxide decomposition. Initiated oxidation of cumene happened at 343 K with the presence of the initiator azodiisobutyronitrile. The concentration of the first compound varied from 1,5·10-4 to 2,5·10-3 mol/l. With a concentration of the first compound 1,25·10-3 and 2,5·10-3 mol/l, the duration of the induction period exceeds 80 min. In the concentration range (1,5÷6,3)·10-4 mol/l the linear change in the duration of the induction period is observed. 4-[3,5-Di(tert-butyl)-4-hydroxyphenyl]-5-aminocarbonyl-6-methyl-3,4-dihydropyrimidin-2-one is a more effective inhibitor than the ionol due to the urea moiety of the dihydropyrimidinone cycle. Confirmation is the notable antioxidant activity of the second compound. In conclusion, 4- [3,5-di (tert-butyl)-4-hydroxyphenyl]-5-ethoxycarbonyl-6-methyl-3,4-dihydropyrimidin-2-one is a bifunctional inhibitor.