Hypobromite, potassium

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. 

Despite the fact that one of the first pteridine syntheses was based on an intramolecular Hofmann carboxamide degradation of pyrazine-2,3-dicarboxamide by action of potassium hypobromite and leads to lumazine (equation 104), (07CB4857), pyrazine derivatives in general have not often been used because of availability problems. The reaction of alkyl... 

Very little is known as yet of the chemistry of cyclopentadienylthallium(I) and the related compounds listed in Table I. The parent compound gives tribromocyclopentane on treatment with bromine and the hexabromo derivative with potassium hypobromite 112). By far the most important use discovered so far for these organothallium(I) compounds is the preparation of metallocenes and cyclopentadiene-transition metal complexes. These preparations are, in general, characterized by manipulative simplicity and high yields, and details of the reactions reported thus far are summarized in Tables II-IV. 

The solution from which excess Br2 is removed by heating must be acidic, otherwise a portion of Br2 shall be fixed in the form of potassium hypobromite (KBrO). 

Oxidation of acetyl- and acetylnitro-substituted thienothiophenes 1 and 2 with ferricyanide or hypoiodite to the corresponding acids was used primarily to confirm the site of electrophilic substitution at position 2 in the thienothiophenes. " Permanganate degrades the thieno[3,2-A]-thiophene (2) ring system, while potassium hypobromite produced bromo derivatives of thieno[2,3-6]thiophene-2-carboxylic acid. ... 

Aminopyridine has been prepared by heating nicotinamide in an alkaline potassium hypobromite solution at 70° by hydrolysis of 8-pyridylurethan with oleum by heating 3-amino-pyridine-2-carboxylic acid at 250° by reduction of 3-nitro-pyridine with zinc and hydrochloric acid and by heating 3-bromopyridine with ammonia and copper sulfate in a sealed tube. ... 

A. J. Balard 6 prepared a soln. of sodium hypobromite, NaOBr, by working in a similar manner to the process employed for the hypochlorite. When bromine is gradually added to soda lye, the bleaching power increases up to a maximum, and after that decreases owing to the conversion of the hypobromite into bromate. A. J. Balard also described a similar product, potassium hypobromite, obtained by the action of bromine on potassium carbonate. 

This reagent, simply prepared by reaction of potassium hypobromite with cyclopenta-diene under PTC690, is a selective bromination agent for activated aromatic systems691 and for a-bromination of ketones692. Upon bromination the reagent is converted to pentabro-mocyclopentadiene. 

Alkynes are simply brominated in high yields by concentrated aqueous potassium hypobromite at 0-40 °C to yield the corresponding 1-bromo-l-alkynes. 

Alanine has been prepared by the catalytic reduction of cyanoacetic esters 1 or salts 2 by heating acrylonitrile,3 /3-amino-propionitrile,4 iw-(/3-cyanoethyl)-amine,5 /3-hydroxypropionitrile, /3-alkoxypropionitriles,7 u.s-(/3-cyanocthyl) ether,8 or bis-(fi-cyano-ethyl) sulfide 8 with aqueous ammonia at 150-225° by the hydrolysis of /3-aminopropionitrile with concentrated hydrochloric acid and subsequent removal of the acid with anion exchange resins.9 The method as described above has been published.10 Additional references to methods of preparation are given in connection with a procedure for the making of /3-alanine from suc-cinimide through the action of potassium hypobromite.11... 

Methyl 3-bromopropiolate has been prepared by esterification of 3-bromopropiolic acid with methanol and sulfuric acid for 6 days (75% yield),4 the starting bromo acid being prepared by bromination of propiolic acid with aqueous potassium hypobromite.6 This reaction is particularly delicate to control, giving erratic results. Moreover, direct bromination of methyl propiolate with sodium hypobromite2 could not be reproduced. 

Potassium hypobromite, KOBr.—The hypobromite can be prepared from the hydroxide or carbonate by the action of bromine, or from the bromide by electrolysis, by methods analogous to those described for sodium hypobromite. 

Sodium aquo ferrocyanide,2 Na3Fe(CN)s.H20, results when sodium nitroprusside reacts with hydroxylamine, etc., or when the salt is oxidised by potassium hypobromite or hydrogen peroxide. 

KBrO, potassium hypobromite KBrOg, potassium bromate... 

Aminopyrazines may be prepared from carbamoylpyrazines by the Hofmann degradation. Gabriel and Sonn (397) first prepared 2-aminopyrazine from 23-dicarbamoylpyrazine with potassium hypobromite through 2-amino-3-carboxy-pyrazine, which was decarboxylated when heated above its melting point (or in refluxing nitrobenzene) (397, 477). 2,3-Dicarbamoylpyrazine with 2 mol of... 

The classical and most standard reaction conditions of the Hofmann rearrangement use sodium or potassium hypobromite (or bromine with sodium or potassium hydroxide) under aqueous conditions. 

Pyridazine-4.5-dicarboxamide affords pyrimido[4,5-r/]pyridazine-2,4-diol [mp >360°C (H20)] in 87% yield when reacted with potassium hypobromite.27... 

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