Hypobromites

Dissolve 36 g. of sodium hydroxide in 160 ml. of water contained in a 500 ml. conical flask, and chill the stirred solution to 0-5° in ice-water. Now add io-8 ml. (32-4 g.) of bromine slowly to the stirred solution exercise care in manipulating liquid bromine ) during this addition the temperature rises slightly, and it should again be reduced to 0-5°. Add a solution of 12 g. of acetamide in 20 ml. of water, in small portions, to the stirred hypobromite solution so that the temperature of the mixture does not exceed 20° the sodium acet-bromoamide is thus obtained in the alkaline solution. Now remove the flask from the ice-water, and set it aside at room temperature for 30 minutes. 

Action of hypobromite. To a solution of urea add sodium hypo-NH2CONH2 + 3NaOBr = Nj + CO2 4- 3NaBr + zHjO... 

Method, There are two standard methods for the estimation of urea, (i) the hypobromite method, (ii) the urease method (p. 519). The chief merit of the hypobromite method is the rapidity of the analysis the results obtained are considered sufficiently accurate for most medical requirements, e.g., for the estimation of urea in urine. For accurate metabolic work, however, the urease method should be employed. 

Urea is decomposed by alkaline sodium hypobromite solution according to the equation ... 

Sodium Hypobromite. Dissolve 200 g. of NaOH in water, make up to I litre, chill in ice water, and slowly add 50 ml. of bromine with stirring. 

The pinacolone may be employed for the preparation of trimethylacetlc acid (plvallc acid) by oxidation with sodium hypobromite solution ... 

By treatment of an amide with sodium hypobromite or sodium hypochlorite solution (or with the halogen and alkali), the amine of one less carbon atom is produced, the net result being the elimination of the carbonyl group. An example is ... 

The hypobromite solution may be prepared by treating 6 ml. of bromine water with dilute sodium hydroxide solution dropwise, until the bromine colour is just discharged. 

Hydrazobenzene may be oxidised to azobenzene by sodium hypobromite solution at 0°. 

Method 2 (from hydrazobenzene). Prepare a solution of sodium hypobromite by adding 10 g. (3-2 ml.) of bromine dropwise to a cold solution of 6-0 g. of sodium hydroxide in 75 ml. of water immersed in an ice bath. Dissolve 9-5 g. of hydrazobenzene (Section IV,87) in 60 ml. of ether contained in a separatory funnel, and add the cold sodimn hypobromite solution in small portions. Shake for 10 minutes, preferably mechanically. Separate the ether layer, pour it into a 100 ml. distilling flask, and distil off the ether by warming gently on a water bath. Dissolve the warm liquid residue in about 30 ml. of alcohol, transfer to a small beaker, heat to boiling on a water bath, add water dropwise to the hot solution until the azobenzene just commences to separate, render the solution clear again with a few drops of alcohol, and cool in ice water. Filter the orange crystals at the pump, and wash with a little 50 per cent, alcohol. Dry in the air. The yield is 8 g. 

Anthranilic acid. This substance, the ortho amino derivative of benzoic acid, may be conveniently prepared by the action of sodium hypobromite (or sodium hypochlorite) solution upon phthalimide in alkaline solution at 80°. The ring in phthalimide is opened by hydrolysis to phthalamidic acid and the latter undergoes the Hofmann reaction (compare Section 111,116) ... 

Good results are obtained by the oxidation of the commercially available cyclo-propyl methyl ketone with sodium hypobromite solution, and the preparation may be regarded as an excellent example of the oxidation of the —COCH, group to — OOH ... 

Sodium hypobromite dissolve 100 g of NaOH in 250 mL of water and add 25 mL of bromine. Sodium nitrate, NaN03—Q.5N 43 g per liter. 

In alkaline solutions, iodine can be oxidized to iodate by sodium hypochlorite or hypobromite, whereas chlorine passed into a solution of iodine and alkah oxidizes ah the way to periodate. 

Basic solutions of lithium bromide can react with oxygen to form hypobromites and bromates under certain conditions. 

Ha.logen Compounds. Fluorine is unreactive toward ozone at ordinary temperatures. Chlorine is oxidized to Cl20 and Cl20y, bromine to Br Og, and iodine to I2O2 and I4O2. Oxidation of haUde ions by ozone increases with the atomic number of haUde. Fluoride is unreactive chloride reacts slowly, ultimately forming chlorate and bromide is readily oxidized to hypobromite (38). Oxidation of iodide is extremely rapid, initially yielding hypoiodite the estimated rate constant is 2 x 10 (39). HypohaUte ions are oxidized to haUtes hypobromite reacts faster than hypochlorite (40). 

Hypochlorite, hypobromite, and hypoiodite are also strong enough to oxidize thiosulfate to sulfate ... 

Cooling water pH affects oxidizing antimicrobial efficacy. The pH determines the relative proportions of hypochlorous acid and hypochlorite ion or, in systems treated with bromine donors, hypobromous acid and hypobromite ion. The acid forms of the halogens are usually more effective antimicrobials than the dissociated forms. Under some conditions, hypochlorous acid is 80 times more effective in controlling bacteria than the hypochlorite ion. Hypochlorous acid predominates below a pH of 7.6. Hypobromous acid predominates below pH 8.7, making bromine donors more effective than chlorine donors in alkaline cooling waters, especially where contact time is limited. 

Oxidation of Chlorides. Hypochlorite can also be formed by the in situ oxidation of chloride ions by potassium peroxymonosulfate [25482-78-4] (36). Ketones like acetone cataly2e the reaction (37). The triple salt of potassium peroxymonosulfate is a stable powder that has been combiaed with chloride salts and sold as toilet bowl cleaners. Bromides can be used ia place of chlorides to form hypobromites, and such combiaations are used to disiafect spas and hot tubs. 

In alkaline solution, bromine reacts rapidly to produce hypobromite. 

It is necessary to maintain this reaction below 0°C to minimize the disproportionation of hypobromite to bromate and bromide. 

Because they are unstable, hypobromites are usually prepared just before use for such jobs as textile bleaching and desizing. In alkaline solutions at 50—80°C bromine reacts to form bromide and bromate. This reaction is reversed in acidic solutions. 

Amides and imides can be N-brominated in the cold by alkah hypobromites (24). 

Hypobromites, the salts of hypobromous acid, do not keep well because they gradually disproportionate to bromide and bromate. Solutions are best prepared as needed from bromine and alkafl with cooling. Because disproportionation is catalyzed by cobalt, nickel, and copper (70), these impurities should be avoided. SoHd alkaline earth hypobromites, or more properly, bromide hypobromites such as calcium bromide hypobromite [67530-61 CaBr(OBr), have been known for many years, but the pure crystalline hydrates sodium hypobromite pentahydrate [13824-96-9] NaOBr 5H20, and potassium hypobromite tribydrate [13824-97-0], KOBr 3H20, were not described until 1952 (71). Hypobromites are strong bleaching agents, similar to hypochlorites. 

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