Tetroxide formation

Early attempts to nitrate thianthrene showed 5-oxidation to proceed more rapidly than C-nitration, both 5-mono- and 5,10-dioxides being available in this way. Production of these, and tri- and tetroxide formation, were already well-studied processes by 1960 (66HC1155). 

Butter, peroxide value, 658, 660, 665 t-Butyl alcohol, tetroxide formation, 740 t-Butyl cumyl peroxide air pollutant, 622 determination, 707 hydroperoxide determination, 685 t-Butyl hydroperoxide (TBHP)... 

The second equilibrium is the more important, giving rise to the nitronium ion, NOj, already mentioned as a product of the dis sociation of dinitrogen tetroxide. Several nitronium salts have been identified, for example nitronium chlorate(VII), (N02) (C104) . If pure nitric acid is dissolved in concentrated sulphuric acid, the freezing point of the latter is depressed to an extent suggesting the formation of four ions, thus ... 

Solutions of dinitrogen tetroxide (the mixed anhydride of nitric and nitrous acids) in sulphuric acid are nitrating agents ( 4.3.2), and there is no doubt that the effective reagent is the nitronium ion. Its formation has been demonstrated by Raman spectroscopy and by cryoscopy ... 

There are two especially important radical—radical reactions of alkylperoxy radicals (28) both beheved to proceed via formation of a transient tetroxide (eqs. 13 and 15). 

Oxidation. Maleic and fumaric acids are oxidized in aqueous solution by ozone [10028-15-6] (qv) (85). Products of the reaction include glyoxyhc acid [298-12-4], oxalic acid [144-62-7], and formic acid [64-18-6], Catalytic oxidation of aqueous maleic acid occurs with hydrogen peroxide [7722-84-1] in the presence of sodium tungstate(VI) [13472-45-2] (86) and sodium molybdate(VI) [7631-95-0] (87). Both catalyst systems avoid formation of tartaric acid [133-37-9] and produce i j -epoxysuccinic acid [16533-72-5] at pH values above 5. The reaction of maleic anhydride and hydrogen peroxide in an inert solvent (methylene chloride [75-09-2]) gives permaleic acid [4565-24-6], HOOC—CH=CH—CO H (88) which is useful in Baeyer-ViUiger reactions. Both maleate and fumarate [142-42-7] are hydroxylated to tartaric acid using an osmium tetroxide [20816-12-0]/io 2LX.e [15454-31 -6] catalyst system (89). 

Nitrogen dioxide rapidly forms an equiUbtium mixture with its dimer, dinitrogen tetroxide (AH g = —28.6 kJ/mol of NO2 consumed). The formation of tetroxide is favored by low temperature and high pressure. 

Formation of Hydrogen Tetroxide. The reaction of hydrogen atoms withHquid ozone at — 196°C proceeds through the intermediate formation of hydroperoxyl radicals forming hydrogen tetroxide, which decomposes on warming to produce equimolar amounts of and O2 (53). 

Because osmium tetroxide is expensive, and its vapors are toxic, alternate methods have been explored for effecting vic-glycol formation. In the aliphatic series, olefins can be hydroxylated with hydrogen peroxide with the use of only a catalytic amount of osmium tetroxide. Anhydrous conditions are not necessary 30% hydrogen peroxide in acetone or acetone-ether is satisfactory. The intermediate osmate ester is presumably cleaved by peroxide to the glycol with regeneration of osmium tetroxide. When this reaction was tried on a A -steroid, the product isolated was the 20-ketone ... 

Other examples are the use of osmium(VIII) oxide (osmium tetroxide) as catalyst in the titration of solutions of arsenic(III) oxide with cerium(IV) sulphate solution, and the use of molybdate(VI) ions to catalyse the formation of iodine by the reaction of iodide ions with hydrogen peroxide. Certain reactions of various organic compounds are catalysed by several naturally occurring proteins known as enzymes. 

Analogous results are obtained in the pyrolysis of 3-alkylidene-2,2,4,4-tetramethylene-thietane dioxides256 (244), 3-hydroxy and 3-keto thietane dioxides (245)191, and 1,3-dithietane dioxides and tetroxides (184b and 7b)192. The extrusion of both CO and S02 and the two S02 moieties in 245b-d and 7b, respectively, to give ethylene, the formation of... 

Figure 6. Formation of S-nitrosoatradne from atrazine and dinitrogen tetroxide...

As with chlorine-containing oxidants, JV-bromo species have been used to oxidize sulphoxides to sulphones (with no bromine incorporation) through the initial formation of a bromosulphonium ion, by nucleophilic attack of the sulphoxide sulphur atom on the electrophilic halogen atom. Such reactions involve JV-bromosuccinimide ° bromamine-T, iV-bromoacetamide ° and iV-bromobenzenesulphonamide. All reported studies were of a kinetic nature and yields were not quoted. In acid solution all oxidations occurred at or around room temperature with the nucleophilic attack on the electrophilic bromine atom being the rate-limiting step. In alkaline solution a catalyst such as osmium tetroxide is required for the reaction to proceed . ... 

On the other hand, manganese tetroxide is so fine that it invades the formation with the filtrate. 

Ruthenium tetroxide can also be used in the oxidation of alkenes. Conditions that are selective for formation of ketols have been developed.36 Use of 1 mol % of RuC13 and five equivalents of KHS05 (Oxone ) in an ethyl acetate-acetonitrile-water mixture gives mainly hydroxymethyl ketones from terminal alkenes. 

For the enthalpies of formation of tetroxides calculated by the method of increments [163,164], see Table 2.14. 

When R is a tertiary alkyl radical, the formed tetroxide decomposes with the formation of two RO and 02. The chain termination includes the following stages in hydrocarbon oxidation by tertiary the C—H bond [12,13,15,165,166] ... 

The reaction between two peroxyl radicals gives a labile compound, which Stockhausen and coworkers [38,39] regard as a hydrotetroxide. The formed tetroxides are very unstable and their decomposition results in the formation of active free radicals. 

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