Vanadium pentoxide peroxide

When heated in the presence of a carboxyHc acid, cinnamyl alcohol is converted to the corresponding ester. Oxidation to cinnamaldehyde is readily accompHshed under Oppenauer conditions with furfural as a hydrogen acceptor in the presence of aluminum isopropoxide (44). Cinnamic acid is produced directly with strong oxidants such as chromic acid and nickel peroxide. The use of t-butyl hydroperoxide with vanadium pentoxide catalysis offers a selective method for epoxidation of the olefinic double bond of cinnamyl alcohol (45). 

Vanadium pentoxide and mercuric oxide were used as catalysts for the hydrogen peroxide oxidation of bis(phenylthio)methane to its monooxide 17a31 (equation 5). From the synthetic point of view, it is interesting to note that vanadium pentoxide, in addition to its catalytic action, functions also as an indicator in this reaction. In the presence of hydrogen peroxide, the reaction mixture is orange while in the absence of hydrogen peroxide a pale yellow colour is observed. Thus, it is possible to perform the oxidation process as a titration ensuring that an excess of oxidant is never present. 

Violence of reaction depends on concentration of acid and scale and proportion of reactants. The following observations were made with additions to 2-3 drops of ca. 90% acid. Nickel powder, becomes violent mercury, colloidal silver and thallium powder readily cause explosions zinc powder causes a violent explosion immediately. Iron powder is ineffective alone, but a trace of manganese dioxide promotes deflagration. Barium peroxide, copper(I) oxide, impure chromium trioxide, iridium dioxide, lead dioxide, manganese dioxide and vanadium pentoxide all cause violent decomposition, sometimes accelerating to explosion. Lead(II) oxide, lead(II),(IV) oxide and sodium peroxide all cause an immediate violent explosion. 

Typical procedure The mole ratio of alkene t-BuOOH catalyst was 10 10 0.25 and 40 mmol of the olefin serving as its own solvent. Thus, 10 mmol of TBHP (80% in di-tert-butyl peroxide) and 0.25 mmol of vanadium pentoxide were added to 50 mmol of the olefin and the reaction mixture was stirred at 60°C under a dinitrogen atmosphere. The products formed were analyzed by GC by comparison of their retention time with those of authentic samples. Good yields of epoxides were obtained only with an excess of olefin to TBHP of 5 1. That the olefin doubles up as the solvent makes for a more practical procedure. Typical results (34) are shown in Table 1 ... 

Urea Peroxide Urea Peroxide Hexamethylenetetramine Hexamethylenetetramine Antimony Trioxide Valeraldehyde Valeraldehyde Valeraldehyde Vinyl Acetate Vanadium Pentoxide Vanadyl Sulfate Vanadium Oxytrichloride Vanadium Pentoxide Vanadium Pentoxide Vanadium Oxytrichloride Vanadyl Sulfate Vanadyl Sulfate Vanadium Oxytrichloride Captan... 

Copper.—Alloys of copper and vanadium are prepared by firing a mixture of vanadium pentoxide, copper oxide, aluminium shot, lime, soda-ash, and fluorspar with the aid of sodium peroxide in a magnesia-lined crucible.2 Electrolytic methods have also been employed, and are applicable for the preparation of other vanadium alloys.3 An alloy containing 3-38 per cent, of vanadium and 96-52 per cent, of copper was found to be harder than copper and could be drawn into wire. An aluminium-copper-vanadium alloy has been prepared.4... 

Concentrated acid solutions of vanadium pentoxide are reduced to the tetravalent state by hydrogen peroxide, the peroxides of sodium, barium, magnesium, and by persulphates of potassium and ammonium.4 Acid solutions of vanadium pentoxide give rise to pervanadic acid with hydrogen peroxide. 

Barium Pyrovanadate, BaaVaO is precipitated on addition of barium chloride to a solution of sodium pyrovanadate or of other vanadates in the presence of ammonia.3 It has more recently been prepared by the action of barium peroxide on vanadium pentoxide.4 It is a white, amorphous powder which melts above 868° C.5... 

It has been shown that in the formation of the red compound in solution each molecule of vanadium pentoxide reacts with two molecules of hydrogen peroxide ... 

Other oxidizing agents have been used. Sodium chlorate with vanadium pentoxide catalyst attacks anthracene readily but is not powerful enough for the conversion of hydrocarbons of the naphthalene and phenanthrene series. An acetic acid solution of 30% hydrogen peroxide has also been used. °... 

Transition metal catalysts not only increase the reaction rate but may also affect the outcome of the oxidation, especially the stereochemistry of the products. Whereas hydrogen peroxide alone in acetonitrile oxidizes alkenes to epoxides [729], osmic acid catalyzes syn hydroxylation [736], and tungstic acid catalyzes anti hydroxylation [737]. The most frequently used catalysts are titanium trichloride [732], vanadium pentoxide [733,134], sodium vanadate [735], selenium dioxide [725], chromium trioxide [134], ammonium molybdate [736], tungsten trioxide [737], tungstic acid [737],... 

Vanadium pentoxide, VjOj (mp 690 °C), is one of the strongest catalysts used for dehydrogenations [478] and oxidations with air or oxygen 479], especially in the gas phase and at very high temperatures. It also catalyzes the hydroxylation of alkenes with aqueous hydrogen peroxide 34]. 

Another kind of anti hydroxylation is the reaction of alkenes with hydrogen peroxide in the presence of vanadium pentoxide, molybdenum trioxide, selenium dioxide, and especially tungsten trioxide (tungstic acid) [131, 144]. Cyclohexene is thus converted into DL-/rarts-l,2-cyclohex-anediol [131],... 

V2O5 Vanadium pentoxide Hydrogen peroxide, water, hydrochloric acid 2.7... 

Obtained by transformation of 4-hydroxycoumarin with tetrabutylammonium bromide promoted by hydrogen peroxide and vanadium pentoxide at 5° for 1 h (55%) [4532]. 

The pentoxides of vanadium, niobium, and tantalum react with hydrogen peroxide to produce per-acids of the general formula HR04. H20. These per-acids increase in stability with increase in atomic weight. Pertantalic acid is a white solid which can be heated to 100° C. without undergoing decomposition. The oxyfluorides of these metals also take up active oxygen to yield peroxyfluorides, which are much better defined in the case of niobium and tantalum than with vanadium. 

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