Bromine production

The substitution is best carried out by boiling A -bromosuccinimide with the olefine in carbon tetrachloride. Succinimide crystallises out from the carbon tetrachloride on cooling w hereas the brominated product remains dissolved in the carbon tetrachloride. 

Halogenated intermediates, dibromoneopentyl glycol [3296-90-0] (DBNPG), and alkoxylated derivatives of tetrabromobisphenol A are used extensively in flame-retardant apphcations. Similar properties can be derived from halogenated dibasic acids, chlorendic anhydride [115-27-5] (CAN), and tetrabromophthahc anhydride [632-79-1] (TBPA). Processes can be used to produce brominated products by the in situ bromination of polymers derived from tetrahydrophthahc anhydride. 

U.S. sodium bromide demand accounts for 8—10% of total bromine production. In 1994 demand is estimated to have been 13,600—17,200 metric tons (5). At mid-1996, the price for technical-grade sodium bromide iu tmckload quantities was 1.54/kg ( 0.70/lb) (6). Manufacturers of sodium bromide iuclude Albemarle, Great Lakes Chemical, Rhc )ne-Poulenc, and Whittaker Corporation. 

Bromine occurs ia the form of bromide ia seawater and ia natural brine deposits (see Chemicals frombrine). Chloride is also present. In all current methods of bromine production, chlorine, which has a higher reduction potential than bromine, is used to oxidize bromide to bromine. 

There are four principal steps in bromine production (/) oxidation of bromide to bromine (2) stripping bromine from the aqueous solution (3) separation of bromine from the vapor and (4) purification of the bromine. Most of the differences between the various bromine manufacturing processes are in the stripping step. 

Figure 3 shows the prices of bromine in tank car quantities from 1976 to 1990. Although the price rose 99% over these years, an average of 5.0% a year, when inflation is taken into account, the price in constant dollars actually fell slightly over that period (51). Estimates of bromine production around the world are shown in Table 3. 

Table 3. Annual Bromine Production in Thousands of Metric Tons ...

Figure 4 shows U.S. bromine production with respect to bromine production in the rest of the world. Israel, especially, has increased its production in recent years (51,52). Between 1976 and 1990 U.S. production fell from 234,000 to 177,000 metric tons Israel s production increased from 23,000 to 135,000 metric tons over that period. 

Halogens attack the ring heteroatom in selenophene and tellurophene. Thus the selenienyl bromide (89) is among the bromination products of benzo[6]selenophene. Tellurophene reacts with halogens to give 1,1-dihalogeno derivatives e.g. 90). 

The reaction of a dibromochalcone with hydroxylamine hydrochloride in pyridine gave three products with the expected 2-isoxazoline product as the predominate compound. A ring bromination product and an isoxazole were also isolated (70UC796). The reaction of hydroxylamine with /S-thiosulfates of propiophenone at reflux produced 3-phenyl-2-isoxazo-line (455). At room temperature a bis-Michael product (456) was produced. The reaction with N -phenylhydroxylamine yielded a mono-Michael type product (457) (74CPB1990). 

I. Too great an excess of water in the reaction mixture appears to result in the formation of higher bromination products. 

The rather large residue of higher-boiling material probably contains higher bromination products of phenol. 

According to this mechanism, a molecule of bromine becomes complexed to the double bond of the alkene, and reorganization of the bonding electrons gives the product. This mechanism can be shown to be incorrect for most alkenes on the basis of stereochemistry. Most alkenes give bromination products in which the two added bromines are on opposite sides of the former carbon-carbon double bond. The above mechanism does not account for this and therefore must be incorrect... 

A company produced bromine in Arkansas and brominated compounds in New Jersey. A risk assessment resulted in a recommendation to consider the transfer of the bromination processes to the bromine production site in Arkansas. Economics and the decrease in risk justified such a transfer and it was done. Although safety was not the only consideration, it was an important factor in this decision. 

Fluorescein Apply sample solution, lead bromine vapor over it or apply 0.1% bromine in chloroform. Various intermediate bromination products are formed with eosin as the final product (Fig. 32). [46]... 

Discovery of Stassfurt salt deposits opened the way for bromine production (for photography and... 

When 10-phenylphenothiazine (104) (and 10-phenylphenoxazine) was brominated in acetic acid a number of products were isolated. Pyridine perbromide, though, only brominated the phenyl substituent (Scheme 47). The suggestion that acetic acid bromination might involve the radical cation of the substrate (104) was confirmed by generating the radical cation of the substrate (104) with perchloric acid prior to bromination. Again a 43% yield of the 3-bromo product and multiple bromination products were observed (Scheme 47). The reaction of 10-phenylphenoxazine with pyridine perbromide appeared to be at least partially electrophilic the products... 

Bromination of 1,3,6-triazacycl[3,3,3]azine (220) occurred initially at the 4-position, then at C-7 and C-9, as predicted (73ACS2421). The 4-cyano-3-methyl derivative gave 7- and 9-brominated products (72ACS624). Similar bromination of ethyl 2-methyl-l,3,4,7-tetracycl[3,3,3]azine-9-carboxylate occurred at the 6-position (73ACS2421). 

The quantity of water added is such that the brominated products do not separate from the aqueous methanol. 

Since thiophene derivatives, heterocyclic aromatic compounds, are sensitive toward electrophilic substitution reactions, the bromination of these compounds generally gives a mixture of mono-, di-, and other poly-substituted bromination products (ref. 19). However, we have recently found that BTMA Br3 is a useful... 

Avramoff et al. have already reported that the reaction of hydrocarbons such as toluene with tetramethylammonium tribromide (TMA Br3) in benzene, in the presence of benzoyl peroxide at room temperature gave benzylic bromination products (ref. 21). However, TMA Br3 is not easy to handle in comparison with the stable BTMA Br3 because of its hydroscopic character. Furthermore, as shown in their literature, a large excess of TMA Br3 is necessary to brominate arenes. 

The bromination products, dibromide in methylene chloride and methoxybromide in methanol, are a mixture of erythro- and threo-diastereoisomers, obtained in a ratio, Erythro/Threo = 70 / 30, which does not depend on the substituents or on the solvent. As expected, the reaction in the protic solvent is fiilly regioselective, i.e. methanol only traps the intermediate... 

One of the key challenges for this process is dealing with the wide range of contaminants in the waste HBr stream. Both inorganic and organic contaminants may be present. These contaminants are typically reactants and products of the upstream bromination process which generated the waste HBr. In addition, they may include corrosion products of upstream equipment or ionic materials present in the water used to scrub the gaseous bromination process effluent. The main concerns about contaminants in the feed streams are their effect on catalyst activity and stability and their effect on bromine product quality. 

Two types of laboratory tests were conducted to evaluate contaminant tests, a catalyst stability test and a high-conversion bromine product test. For catalyst stability testing, only a small amount of catalyst was used (1.5 g) to ensure incomplete conversion of the HBr. If a feed contaminant causes catalyst deactivation, it is apparent as an immediate decrease in conversion. If an excess of catalyst was used instead, even if deactivation occurred at the inlet of the bed, it may not be detected until the region of deactivation moves considerably downstream. This could take many hours or days. 

The high-conversion bromine product quality tests at 300°C and 335°C gave greater than 99 % HBr conversion. Analysis of the resulting bromine showed no detectable chlorine. 

The phenol-contaminated sample was unique in yielding bromine containing none of the starting contaminant. Analysis of the bromine by FT-IR and INMR showed a complex mixture of brominated phenols and small amounts of other brominated hydrocarbons. The absence of phenol in the bromine product is not surprising, since phenol reacts with bromine at room temperature to make predominantly tribromophenol. 

For the organic contaminants, the required bromine product quality wilt also be site specific. If the catalytic oxidation unit is dedicated to a single bromination process, phase separation and drying may be the only purification required. Contaminants in the recovered bromine which are either the starting materials or products of the original bromination reaction should not present a problem if present in bromine recycled to the bromination reactor. In this case, the catalytic reactor would be operated to minimize the formation of undesirable brominated byproducts. For example, if phenol is present in the waste HBr from a tribromo-phenol manufacturing process, minor tribromophenol contamination of the bromine recycled to the reactor should not be a problem. Similarly, fluorobenzene in bromine recycled to a fluorobenzene bromination process should not present a problem. 

Manufacturers of brominated products are facing increasing economic, environmental and legislative pressure to improve their processing with respect to the effluent discharged. 

Temperature programmed GC (Fig. 2) separates these components as well as a cyclic formal. The mono, di and tri brominated products of 1 require higher temperatures to elute in a reasonable time more than the column can withstand. TMS derivatives do not require temperatures quite so high (Fig. 3). Using this technique for quantitation, however, is complicated by the decreasing sensitivity of the FID to increasing bromine content. 

With deactivated aromatic derivatives, such as nitrobenzene, BrFs and Br2 is an effective reagent, gives the meta-brominated product. ... 

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