Hydrogen peroxide small amounts

Also obtained by dehydrogenation of propiognaiacone in aqneous solution with hydrogen peroxide (small amount) [8399]. 

As an alternative to depolymerisation, ring expansions, starting from a common intermediate, have been developed. Hydrogen peroxide adds regiospecificallyto the bicyclic dihydropyran. The hydroperoxide reacts with a second molecule of the educt. Thermolysis leads eventually to exaltolide, with xylene serving as the hydrogen donor. Small amounts of 15-pentadec-ll-enolide are formed as a by-product (Tab. 3.6). 

However, it is possible that the oxidation involves H radicals. At T > 330 °C and atmospheric pressure, a CH4— 2—H2 mixture is converted on the Feo.5Alo5 4 catalyst into methanol with a selectivity of 28% at a conversion of 0.4—1.5%. In situ IR spectra showed the presence of absorption bands of surface peroxides at a frequency of 895 cm . At T > 530 °C, in the absence of hydrogen, only small amounts of formaldehyde were formed. It was assumed that the active site was a tetrahedrally coordinated Fe (HI) ion, on which the following reactions occurred ... 

Detecting the presence of small, even invisible, amounts of blood is routine. Physical characteristics of dried stains give minimal information, however, as dried blood can take on many hues. Many of the chemical tests for the presence of blood rely on the catalytic peroxidase activity of heme (56,57). Minute quantities of blood catalyze oxidation reactions between colorless materials, eg, phenolphthalein, luco malachite green, luminol, etc, to colored or luminescent ones. The oxidant is typically hydrogen peroxide or sodium perborate (see Automated instrumentation,hematology). 

Propellant. The catalytic decomposition of 70% hydrogen peroxide or greater proceeds rapidly and with sufficient heat release that the products are oxygen and steam (see eq. 5). The thmst developed from this reaction can be used to propel torpedoes and other small missiles (see Explosives and propellants). An even greater amount of energy is developed if the hydrogen peroxide or its decomposition products are used as an oxidant with a variety of fuels. 

Peroxidic Compounds. When hydrogen peroxide is added to a solution of titanium(IV) compounds, an intense, stable, yellow solution is obtained, which forms the basis of a sensitive method for determining small amounts of titanium. The color probably results from the peroxo complex [Ti(02)(0H)(H20)J, and crystalline salts such as K2[Ti(02)(S0 2] H20 can be isolated from alkaline solutions. The peroxo ligand is bidentate the two oxygen atoms ate equidistant from the titanium (98). 

The preparation of neopentyl alcohol from diisobutylene herein described represents an example of acid-catalyzed addition of hydrogen peroxide to a branched olefin, followed by an acid-catalyzed rearrangement of the tertiary hydroperoxide formed. In addition to neopentyl alcohol, there are formed acetone and also small amounts of methanol and methyl neopentyl ketone by an alternative rearrangement of the hydroperoxide. 

A mixture of A,A-dimethylcyclohexylmethylamine (49.4 g, 0.35 mole. Chapter 2, Section I), 30% hydrogen peroxide (39.5 g, 0.35 mole) and 45 ml of methanol is placed in a 500-ml Erlenmeyer flask, covered with a watch glass, and allowed to stand at room temperature. After 2 hours, and again after an additional 3 hours, 30% hydrogen peroxide (39.5-g portions each time) is added with swirling. The solution is allowed to stand at room temperature for an additional 30 hours, whereupon excess peroxide is destroyed by the cautious addition (swirling) of a small amount of platinum black. Cessation of oxygen evolution indicates complete decomposition of the excess peroxide. 

Most of the controlled corrosion studies on beryllium have been carried out in the USA in simulated reactor coolants. The latter have usually been water, aerated and de-aerated, containing small amounts of hydrogen peroxide and at temperatures up to 300-350°C. Many variables have been examined, covering surface condition, chemical composition, temperature, pH, galvanic effects and mechanical stress . 

In some cases, a small amount of nitric acid, HN03, or hydrogen peroxide, H202, is added to the solution in order to accelerate the dissolution of the metal. Heating the solution increases dissolution rates as well. Taking into... 

Discussion. With an acidic titanium(IV) solution hydrogen peroxide produces a yellow colour with small amounts oftitanium(up to 0.5 mg ofTiOz permL), the intensity of the colour is proportional to the amount of the element present. Comparison is usually made with standard titanium(IV) sulphate solutions a method for their preparation from potassium titanyl oxalate is described below. The hydrogen peroxide solution should be about 3 percent strength (ten volume) and the final solution should contain sulphuric acid having a concentration from about 0.75 to 1.75M in order to prevent hydrolysis to a basic sulphate and to prevent condensation to metatitanic acid. The colour intensity increases slightly with rise of temperature hence the solutions to be compared should have the same temperature, preferably 20-25 °C. 

The distilled product can be used as a catalyst, although it usually has a relatively strong phenylphosphine odor. It is quite deliquescent, and it has not been satisfactorily recrystallized. If rigorous purification and deodorization are desired, the product is dissolved in water, a small amount of hydrogen peroxide is added to oxidize the phosphines, the solution is reneutralized, saturated with salt, and extracted with chloroform, and the product is refractionated. One cycle is normally enough. Pure product is essentially odorless, very hygroscopic, and soluble in polar solvents. 

A 250-mL, two-necked, round-bottomed flask equipped with a magnetic stirbar, thermometer, and a reflux condenser fitted with a rubber septum and balloon of argon is charged with a solution of methyltrioxorhenium (MTO) (0.013 g, 0.05 mmol, 0.1% mol equiv) in 100 mL of methanol (Note 1). Urea hydrogen peroxide (UHP) (14.3 g, 152 mmol) is added (Notes 1, 2, 3, 4), the flask is cooled in an ice bath, and dibenzylamine (9.7 mL, 50.7 mmol) is then added dropwise via syringe over 10 min (Notes 1, 5). After completion of the addition, the ice bath is removed and the mixture is stirred at room temperature (Note 6). A white precipitate forms after approximately 5 min (Note 7) and the yellow color disappears within 20 min (Note 8). Another four portions of MTO (0.1% mol equiv, 0.013 g each) are added at 30-min intervals (2.5 hr total reaction time). After each addition, the reaction mixture develops a yellow color, which then disappears only after the last addition does the mixture remain pale yellow (Note 9). The reaction flask is cooled in an ice bath and solid sodium thiosulfate pentahydrate (12.6 g, 50.7 mmol) is added in portions over 20 min in order to destroy excess hydrogen peroxide (Note 10). The cooled solution is stirred for 1 hr further, at which point a KI paper assay indicates that the excess oxidant has been completely consumed. The solution is decanted into a 500-mL flask to remove small amounts of undissolved thiosulfate. The solid is washed with 50 mL of MeOH and the methanol extract is added to the reaction solution which is then concentrated under reduced pressure by rotary evaporation. Dichloromethane (250 mL) is added to the residue and the urea is removed by filtration through cotton and celite. Concentration of the filtrate affords 10.3 g (97%) of the nitrone as a yellow solid (Note 11). 

FIGURE 13.33 A small amount of catalyst—in this case, potassium iodide in aqueous solution—can accelerate the decomposition of hydrogen peroxide to water and oxygen, (a) The slow inflation of the balloon when no catalyst is present, (b) Its rapid inflation when a catalyst is present. 

The addition of hydrogen halides to simple alkenes, in the absence of peroxides, takes place by an electrophilic mechanism, and the orientation is in accord with Markovnikov s rule. " When peroxides are added, the addition of HBr occurs by a free-radical mechanism and the orientation is anti-Markovnikov (p. 985). It must be emphasized that this is true only for HBr. Free-radical addition of HF and HI has never been observed, even in the presence of peroxides, and of HCl only rarely. In the rare cases where free-radieal addition of HCl was noted, the orientation was still Markovnikov, presumably beeause the more stable product was formed. Free-radical addition of HF, HI, and HCl is energetically unfavorable (see the discussions on pp. 900, 910). It has often been found that anti-Markovnikov addition of HBr takes place even when peroxides have not been added. This happens because the substrate alkenes absorb oxygen from the air, forming small amounts of peroxides... 

It is well established that aerobes constantly produce small amounts of oxygen-derived species, such as the superoxide radical (02 ), hydrogen peroxide (H2O2) and hypochlorous acid (HOCl), the latter being generated by... 

---