Oxygen activation on metallic centers and oxidizing abilities of such oxygen

It was shown that metallcontaining peroxides such as XOOOBu-t [X = (t-BuO)₂Al, (t-BuO)₃Ti] generate molecular oxygen in the electron-excited singlet state (¹O₂). These ozonides and η²-peroxocomplex Ph₃Bi(η²O₂) demonstrate high oxidative activity towards some classes of organic substances under mild conditions (20 °C).     

Reaction of Organoelement Hydrides R<Subscript>3</Subscript>EH (E = Si,Ge) with Metal <Emphasis Type="Italic">tert</Emphasis>-Butylate (M = Al,Ti)-<Emphasis Type="Italic">tert</Emphasis>-Butyl Hydroperoxide Oxidative Systems

Trialkyl(aryl)silanes and -germanes effectively react with metal (Al, Ti) tert-butylate-tert-butyl-hydroperoxide under mild conditions (room temperature, benzene or tetrachloromethane) mainly by the element-hydrogen bond. The character of the products depends on the nature of the element, the structure of the radical bound to it, and the solvent. The process is radical in nature. It includes the stages of formation of element-centered radicals and their reaction with the oxygen generated by the system. The intermediate organometallic peroxides can also acts as oxidants for the element (Si, Ge)-hydrogen bonds.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 7, 2005, pp. 1161–1170.Original Russian Text Copyright © 2005 by Stepovik, Gulenova, Martynova, Skvortsov, Cherkasov.     

Reaction of zirconium alkoxides with tert-butyl hydroperoxide. Oxidative ability of the Zr(OBu-t)4-t-BuOOH system

Oxidation of the isopropoxy group in the Zr(i-PrO)₄·i-PrOH complex involves both direct reaction with tert-butyl hydroperoxide and intermediate formation of zirconium peroxy compound. Zirconium tetra-tert-butoxide reacts with tert-bytyl hydroperoxide to form metal-containing peroxide and trioxide. Decomposition of the latter leads to oxygen evolution and is accompanied by radical formation. The alkoxyl and peroxyl radicals formed were identified by ESR spectroscopy. The nature of the oxidant (oxygen, zirconium-containing peroxide and-trioxide) in the Zr(OBu-t)₄-t-BuOOH system is determined by the structure of the substrate molecule.     

Reaction of Unsaturated Esters with the Oxidative System Aluminum Tri-tert-Butoxide-tert-Butyl Hydroperoxide

Unsaturated esters containing double bonds in the acyl (methyl acrylate) or in the alcohol (vinyl and allyl acetates) fragments are cleaved under mild conditions (20°C) by the system aluminum tri-tert-butoxide-tert-butyl hydroperoxide to give tert-butyl esters of peroxycarboxylic acids and unsymmetrical aluminum alkoxides. The double bond in the acyl fragment is inert to this oxidation system. Vinyloxy- and allyloxy derivatives are oxidized to hydroxyethanal and (hydroxymethyl)oxirane, respectively. Carbonhydrogen bonds are oxidized only in allyl acetate.     

Oxidizing properties of the tert-butyl hydroperoxide-tetra-tert-butoxychromium system

tert-Butyl hydroperoxide reacts with the tetra-tert-butoxychromium by oxidizing the latter to chromyl CrV=O (C₆H₆, 20°C). At t-BuOOH-Cr(OBu-t)₄ ratio of 2: 1 or higher, oxygen is released. The occuring processes include the formation of chromium-containing peroxides and peroxytrioxydes. The t-BuOOH-Cr(OBu-t)₄ system oxidizes aromatic hydrocarbons of various structures (anthracene, 9,10-dimethylanthracene, 1,1-diphenylethylene, alkylarenes), as well as primary and secondary alcohols. Depending on the structure of the substrate, the oxidants are: in situ generated oxygen including that in the singlet state, peroxy radicals, or chromium-containing peroxides.     

Angular distribution of electrons from powerful accelerators

A technique for measuring the angular distribution of electrons escaping from the center of the window of the IGUR-3 and ÉMIR-M powerful accelerators (designed at the All-Russia Institute of Technical Physics, Russian Federal Nuclear Center) into ambient air is presented, and measurement data are reported. The number of electrons is measured with cable detectors (the solid angle of the collimator of the detector is ≈0.01 sr). The measurements are made in three azimuthal directions in 120° intervals in the polar angle range 0–22°. The angular distributions of the electrons coming out of the accelerators are represented in the form of B splines.     

Effect of Radio-Frequency and Ionizing Radiation on the ATmega8515 Microcontroller

Technical Physics - Effect of ultrabroadband radiation and bremsstrahlung on a complicated device (ATmega8515) placed in a radio-transparent housing is studied. Similar results are obtained in the...     

System vanadium alkoxy compound-<Emphasis Type="Italic">tert</Emphasis>-butyl hydroperoxide-oxidant of hydrocarbon C-H bonds

Vanadium alkoxy compounds [(t-BuO)₄V, (t-BuO)₃VO] react with tert-butyl hydroperoxide (C₆H₆, 20°C) to liberate oxygen, partly in the singlet form, and to form alkoxyl and peroxyl radicals via the intermediacy of vanadium peroxides and trioxide. These systems are capable of oxidizing hydrocarbon C-H bonds. The process is radical in nature and involves formation of carbon-centered radicals and their reaction with oxygen generated in the systems. Vanadium-containing peroxides, too, take part in the oxidation reaction.     

Specific features of the reaction of vanadyl acetylacetonate with <Emphasis Type="Italic">tert</Emphasis>-butyl hydroperoxide

Reaction of vanadyl acetylacetonate with tert-butyl hydroperoxide (benzene, 20°C) at any molar ratio leads to the elimination of ligand and its oxidation mainly to CO₂ and acetic acid. At the (acac)₂VO: t-BuOOH ratio above 1:10 liberation of oxygen partially in the singlet state takes place.     

Oxidation of alkylarene C-H Bonds by tert-butyl hydroperoxide in the presence of cobalt, chromium, and vanadium acetylacetonates

Cobalt, chromium, and vanadium acetylacetonates catalyze efficient hydroperoxide oxidation of alkylarenes under mild conditions (20°C). The process takes place with either conservation, or destruction of carbon backbone of the hydrocarbon. Oxidizing agents are oxygen generated in the system, as well as tert-butylperoxy radicals. In the formation of end products alkylperoxy radicals originating in the substrates, tert-butylperoxy radicals, as well as metal-containing peroxides are involved. For the oxidative degradation processes a recombination reaction of the alkylperoxy radicals is suggested with the intermediate formation of 1,2-dioxetanes.