Bromination methods

For those without a fume cupboard, proceed as below. For those with a fume cupboard, the second bromination method is recommended. 

Table I. Comparison of brominating methods of preparation of bromocriptine 2... 

Actually, at industrial scale, we use a direct bromination method with bromine in methanol at low temperature (eqn. 4). 

Among the most important indirect methods of analysis which employ redox reactions are the bromination procedures for the determination of aromatic amines, phenols, and other compounds which undergo stoichiometric bromine substitution or addition. Bromine may be liberated quantitatively by the acidification of a bromate-bromide solution mixed with the sample. The excess, unreacted bromine can then be determined by reaction with iodide ions to liberate iodine, followed by titration of the iodine with sodium thiosulphate. An interesting extension of the bromination method employs 8-hydroxyquinoline (oxine) to effect a separation of a metal by solvent extraction or precipitation. The metal-oxine complex can then be determined by bromine substitution. 

K. H. Meyer s bromine method 1 makes it possible to determine the enol content in almost all solutions of tautomeric substances. 

In respect of their properties, conditions of rearrangement, and reactions, we simply refer to what was said about the keto-enol change. Here, also, the bromine method enables the points of equilibrium to be determined quantitatively. The oldest and most important example of desmotropy in nitro-compounds was found in phenylnitromethane,... 

Note 2 In order to convert DPhA to its hexanitro-derivative, NC must be present in sample in quantity 1 g per each lOmg of DPhA. If NC is absent, use 20ml of fuming nitric acid in lieu of acid of sp gr 1.42 Note 3- Centralices, diphenylurea and diphe-nylurethane interfere with nitration test Test 2- Gravimetric Bromination Method,... 

Note A modification of "gravimetric bromi-nation method , devised by Apatoff and Cohen of Frankford Arsenal is described in Vol 2 of Encycl, p 032 and also in Ref 29, pp5—6 Test 3. Volumetric Bromination Method. 

Bromination Method. Transfer an accurately weighed 0.9—l.Og sample to a 250ml iodine flask provided with a glass stopper and dissolve it. in 25ml of chloroform. Add 60ml of glac AcOH, followed by exactly 10.0ml of... 

Dr H. Walter (Ref 7) suggests the bromination method, simply by adding bromine water. This gives 2,4,6-tribromoanisole. Det its mp(87-8°) and mixed mp... 

In the bromine method, bromine in carbon tetrachloride was added to the gasolines in a test tube. Heating assured complete conversion to lead bromide. The resulting lead bromide precipitate was dissolved with dilute —1M nitric acid. The mixture was centrifuged, the organic layer discarded, and the aqueous solution was adjusted for M.S. analyses. Either of the procedures is satisfactory, but the bromine method is much easier, faster, and has less possibility for contamination. 

The novel bromination method also works well for carbazole (Fig. 9). Because there is little influence on the reactivity of the second benzene ring when the first is brominated monobromination is not particularly selective. However, dibromination is highly selective, as is tribromination. Tetrabromination is very slow, even with excess NBS. The behaviour of N-ethylcarbazole is similar, except that monobromination is slightly less selective (50% 3-bromo-lV-... 

Central ite 1 Analytical Procedures. Centr 1 can be detected by various colorimetric tests, such as described in Refs 1,6,12,24, 28 Sc 33. Some other qualitative tests are given in Ref 13. Quantitative detns of Centr 1 by bromination methods are described in Refs 4,5,7,9,10,14,16,17,20,27,34 Sc 35. Chromatographic and spectrophotometric methods are found in Refs-11,15,18,21,22,23,24, 29,30,32 Sc 33. Other quantitative methods, including polarographic, are in Refs 2,7a,20a,25, 26,27 Sc 30. X-ray diffraction spectra data are given in Ref 19. Detns of stabilizing action of Centr 1 by methods of Taliani and Thomas are discussed in Refs 3 8... 

NG 43.00, DEtPh 3.00, K sulfate 1,25 EtCentr 0.60%] 19)A.M.Soldate R.M.Noyes, AnalChem 19, 442-4(1947)(X-ray diffraction spectra for Centr 1) 20)I.S.Hirschhom, AnalChem 19, 880-2(1947) [Rapid method of detn of Centr 1 NG in rocket propints. Both ingredients are extracted with 84% AcOH and then Centr is detd by bromination method of Waugh et al(See Ref 16)] 20a)T.C.J. 

Recently, Eisch s142 bromination method (Br2-CCl4-pyridine) has been applied to all the 1, -naphthyridines (x = 5, 6, 7, 8).90 1,5-Naphthyridine afforded 3-bromo- (27%) and 3,7-dibromo-l,5-naphthyridine (10%). The 3-bromo-, 8-bromo-, and 3,8-dibromo-1,6-naphthyridines were obtained from 1,6-naphthyridine.96 1,7-... 

C6H2 Br3NH2 +6KCI+3H2 0+3HBr The original bromination method was described in 1876 by Koppeschaar(Ref 1)... 

L.D.Johnson et al, AnalChem 27,1494—8 (1955) and 28,392(1956) (Bromination method is not always applicable in analysis of mixts of nitrated aniiine and phenols) lijGrganic Analyses,Interscience,NY,vol 3(1956)... 

Sodium V-nitrosohydroxylamine-V-sulfonate, 5 119 Sodium paraperiodate (orthoperiodate) (Na3H2I06), by chlorine method, 1 169 by persulfate method, 1 170 by sodium iodide-bromine method, 2 212... 

Poly(4-vinylpyridine)-supported bromate in nonaqueous solution has been used in the bromination of aromatic compounds with potassium bromide <2005SC1947>. This bromination method is simple, efficient, mild, and selective for methoxyarenes, anilines, and phenols. 

Unsaturation. The cellulose molecule is a saturated one. Cellulose nitrate as treated in the graft copolymerization reaction conditions in the absence of monomer was found to be unsaturated by bromination method (Table XI). The amount of unsaturation was estimated as 0.14 per anhydroglucose unit. 

Straight-line relationships were obtained between the accessibilities by the bromine method and the IR crystallinity indices and the wide angle x-ray scattering (WAXS) indices for 16 native and regenerated celluloses with accessibilities ranging from 70 to 6% (See Table 5.3 and Figure 5.21 and Figure 5.22). 

The first use of a bromate-bromide mixture as a source of bromine was by Koppescbaar, who devised the classical bromination method for phenol. The method is still in use today and has been applied to a wide variety of organic com-poimds. Three types of error can be recognized (7) oxidation of readily oxidized substances such as o- and p-aminophenols (2) precipitation of incompletely bromin-ated products, which occurs especially with parasubstituted compounds such as p-nitroaniline and p-iodoaniline and (5) replacement of certain groups such as —COOH, —CHO, or —SO3H by bromine. 

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