Hydrogen peroxide disappearance

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). 

In solutions of pH > 3, when the rate of reduction of peroxy acid is much lower, the induced disappearance of hydrogen peroxide will be considerably reduced. 

Preparation of Benzoyl Peroxide.1—Hydrogen peroxide (50 c.c. of about 10 per cent aqueous solution) kept well cooled in ice and continually shaken (preferably in a glass-stoppered bottle) is treated alternately with 4 A-sodium hydroxide solution and benzoyl chloride, added each a few drops at a time the solution is maintained faintly alkaline throughout. After about 30 c.c. of alkali and 15 g. of benzoyl chloride have been used up, the hydrogen peroxide has been decomposed and the benzoyl peroxide has separated in crystalline flocks, while the odour of the chloride has almost completely disappeared. The peroxide is filtered with suction, washed with water, and dried. Yield 10-12 g. Crystallised from a little alcohol, with which it should be boiled for a short time only, the substance forms beautiful colourless prisms. Melting point 106°-108° decomp. Heat a small quantity rapidly in a dry test tube over a naked flame. An especially pure product is obtained when a 1 von Pechmann and Vanino, Ber., 1894, 27, 1510. 

Figure 1. The measured dry weight after hydrogen peroxide scission of sulfonated PSDVB XZ% DVB cation exchange resin) is seen to decrease linearly with reaction time. The time obtained by extrapolating to zero weight corresponds to visual observation degelation indicated by the disappearance of the resin particles.

In this representation of the reaction the hydrogen chlorine chains are cut off short by the disappearance of a hydrogen atom accompanied by the formation of one molecule of water and one half molecule of hydrogen peroxide. However, Salley and Bates have demonstrated that. 

Preparation of Manganese(IV) Oxide Sol. Add a 2% hydrogen peroxide solution to 5 ml of a potassium permanganate solution containing 14 g of salt per litre of solution until the violet colour disappears. Write the equation of the reaction. To determine the end of the reaction, proceed as follows add a few drops of a saturated sodium chloride solution to a small sample and heat it. If a violet colour is noticeable, add more hydrogen peroxide solution to the main solution. 

The faster disappearance of hydrogen peroxide at the pic darret can be explained by the failure of Reaction 3, owing to the exhaustion of oxygen while Reaction 14 continues. 

DISSOLVE A FEW CRYSTALS OF POTASSIUM PERMANGANATE IN WATER. ADD TINY AMOUNT OF SODIUM BISULFATE [TO MAKE SOLUTION SOUR). POUR IN A LITTLE HYDROGEN PEROXIDE (HjOj). COLOR DISAPPEARS AND OXYGEN IS LIBERATED. 

The properties, crystal habit, and x-ray pattern of tungsten(IV) dichloride oxide are very similar to those of molybdenum(IV) dichloride oxide.8 Stoichiometric tungsten(IV) dichloride oxide, which forms gold-brown needles, is stable under atmospheric conditions and is not attacked by water, dilute or concentrated cold acids, ammonia, or organic solvents, such as acetone, ethanol, 2-methoxyethanol, chloroform, and diethyl ether. However, it decomposes in a solution of sodium hydroxide and forms a black precipitate, which disappears when hydrogen peroxide is added and yields a clear, yellow solution. The density of tungsten(IV) dichloride oxide, determined pycnometrically as previously mentioned, is 5.92 g./cc. 

To a stirred suspension of diisopinocampheylborane (50 mmol) (1) in tetra-hydrofuran (18 ml) is added 4.5 ml of (Z)-but-2-ene. The reaction mixture is stirred at 25 °C for 4.5 hours. The solid diisopinocampheylborane disappears and the formation of the trialkylborane is complete. The organoborane is treated with 4 ml of methanol, followed by 18.3 ml of 3 m sodium hydroxide and the careful addition of 20 ml of 30 per cent hydrogen peroxide, maintaining the temperature of the reaction below 40 °C. The reaction mixture is further stirred at 55 °C for 1 hour, cooled, and extracted with ether (3 x 50 ml). The extract is washed successively with water (2 x 25 ml) and brine (3 ml) and dried over magnesium sulphate. The organic layer is carefully fractionated to provide butan-2-ol, b.p. 96-98 °C, 2.9 g (73%), purity > 95 per cent. The last traces of impurities are removed by preparative g.l.c. (2) to yield (R)-butan-2-ol, [a] 3 —13.23° (neat), ee 98.1 per cent. 

Although Fenton (1894) studied the violet color in caustic alkali during oxidation of tartaric and racemic acids by ferrous salt and hydrogen peroxide, no reaction kinetic model was offered. Fenton reported that the color disappeared when acid was added. Also, it has been observed that fresh external air is more active than room air. Fenton performed different experiments using various amounts of ferrous and hydrogen peroxides and... 

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