Bromine applications

There are in fact some bromine applications that are not questioned from an environmental point of view. Bromine has a similar usage to chlorine for water disinfection. Silver bromide is used as a Hght-sensitive substance in photographic emulsions. A quarter of aU bromine used finds its way down into boreholes in oilfields, where calcium and zinc bromide solutions are used as drilling fluids. In high concentrations, the liquids are heavy and exert a high hydrostatic pressure that prevents the very disturbing blow-out situations. 

HOBr is typically reported in terms of available chlorine, because it is usually measured using a chlorine procedure. In order to convert the measurement into terms of bromine, the result should be multiplied by a factor of 2.25 and reported as ppm bromine. Most bromine applications use a mixture of chlorine and bromine. Therefore, residual values are typically left in terms of chlorine to avoid confusion. Do not report ppm bromine without running the conversion and making sure the customer understands the difference and wants it reported as bromine. 

The reaction is applicable to the preparation of amines from amides of aliphatic aromatic, aryl-aliphatic and heterocyclic acids. A further example is given in Section IV,170 in connexion with the preparation of anthranilic acid from phthal-imide. It may be mentioned that for aliphatic monoamides containing more than eight carbon atoms aqueous alkaline hypohalite gives poor yields of the amines. Good results are obtained by treatment of the amide (C > 8) in methanol with sodium methoxide and bromine, followed by hydrolysis of the resulting N-alkyl methyl carbamate ... 

Another method for the hydrogenoiysis of aryl bromides and iodides is to use MeONa[696], The removal of chlorine and bromine from benzene rings is possible with MeOH under basic conditions by use of dippp as a ligand[697]. The reduction is explained by the formation of the phenylpalladium methoxide 812, which undergoes elimination of /i-hydrogen to form benzene, and MeOH is oxidized to formaldehyde. Based on this mechanistic consideration, reaction of alcohols with aryl halides has another application. For example, cyclohex-anol (813) is oxidized smoothly to cyclohexanone with bromobenzene under basic conditions[698]. 

At elevated temperatures (250-400°C) bromine reacts with thiazole in the vapor phase on pumice to afford 2-bromothiazole when equimolecu-lar quantities of reactants are mixed, and a low yield of a dibromothiazole (the 2,5-isomer) when 2 moles of bromine are used (388-390). This preferential orientation to the 2-position has been interpreted as an indication of the free-radical nature of the reaction (343), a conclusion that is in agreement with the free-valence distribution calculated in the early application of the HMO method to thiazole (Scheme 67) (6,117). 

D. Price, B. Iddon, and B. J. Wakefield, eds.. Bromine Compounds Chemistry and Applications, Elsevier, Amsterdam, the Nethedands, 1988. 

Benzo[b]furan, 2,3-dihydro-2-phenyl-synthesis, 4, 697 Benzo[b]furan, 2,3-dihydroxy-tautomerism, 4, 37 Benzo[6]furan, 4,6-dimethoxy-acylation, 4, 606 Benzo[6]furan, 2,3-dimethyl-acetylation, 4, 606 bromination, 4, 605 photooxygenation, 4, 642 Benzo[b]furan, 5,6-dimethyl-2,3-diphenyl-applications, 4, 709 Benzo[b]furan, 1,3-diphenyl-vertical ionization potential, 4, 587 Benzo[b]furan, 2-ethoxy-5-hydroxy-synthesis, 4, 127... 

Quinoxaline, 6-hydroxy-applications, 3, 195 tautomerism, 3, 173-174 Quinoxaline, isopropyl-oxidation, 3, 169 Quinoxaline, 2-methyl-bromination, 3, 167-168 oxidation, 3, 169 reactions... 

Me3SiCH2CH=CH2i TsOH, CH3CN, 70-80°, 1-2 h, 90-95% yield. This silylating reagent is stable to moisture. Allylsilanes can be used to protect alcohols, phenols, and carboxylic acids there is no reaction with thiophenol except when CF3S03H is used as a catalyst. The method is also applicable to the formation of r-butyldimethylsilyl derivatives the silyl ether of cyclohexanol was prepared in 95% yield from allyl-/-butyldi-methylsilane. Iodine, bromine, trimethylsilyl bromide, and trimethylsilyl iodide have also been used as catalysts. Nafion-H has been shown to be an effective catalyst. 

Although not so generally applicable for the preparation of dicyclopentadienyl metal compounds as the sodium cyclopenta-dienide method, the amine procedure represents the simplest preparation of ferrocene. The amine procedure can also be employed for dicyclopentadienylnickel (about 80% yield), using nickel bromide obtained by the action of bromine on nickel metal powder and 1,2-dimethoxyethane as the solvent. The method of preparation given here is a modified version of that originally described. ... 

An important application of the allylic bromination-dehydrobromination approach is the formation of the A -diene system e.g. 110) in vitamin D synthesis. Dehydrobromination of the A -7-bromo system in the presence of mercuric chloride gives a high yield of A -diene. ... 

Vilsmeier-Haack and Friedel-Crafts reactions, bromination, debromination, debenzylation in indole series and their synthetic application 99YZ35. 

By application of the Hell-Volhard-Zelinskii reaction,an a-hydrogen of a carboxylic acid 1 can be replaced by bromine or chlorine to give an a-bromo-or a-chlorocarboxylic acid 2 respectively. 

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