Additives bromine

Bromine monofluoride [13863-59-7], BrF, can be prepared by the direct reaction of Br2 and F2, but because it readily disproportionates it has never been prepared in pure form (57). However, BrF can be prepared in situ by the reaction of Br2 with AgF in benzene (58) or by the reaction of A/-bromoacetamide and HF in ether (59). BrF adds to simple alkenes at room temperature to give products of trans-addition. Bromine trifluoride [7787-71-5], BrF, can be formed from gaseous fluorine and Hquid bromine (60). Bromine pentafluoride [7789-30-2], BrF, is formed from the reaction of BrF vapor with gaseous fluorine at 200°C (60). The tri- and pentafluorides are commercially available. As strong fluorinating agents they are useful in... 

Reactivity of electrophilic addition (bromination) of MeO CCCCOjMe [33] suggests the predominance of the perpendicular conformation. Triple bonds are usually less reactive toward electrophiles than double bonds. PhCCH is brominated 3,000 times more slowly than PhCH=CH2. However, MeO CCCCO Me is brominated... 

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. 

In addition, brominated derivatives of alkylphenols (BrNPnEO and BrNPnEC) can be formed during chlorine disinfection of water if... 

CASRN 106-40-0 molecular formula CeHeBrN FW 172.02 Chemical/Physical. Hypochlorous acid reacted with p-bromoaniline forming bromochloro-aniline, bromodichloroaniline, dibromoaniline, and dibromochloroaniline. The displacement of bromine atom by chlorine yields hypobromous acid which then displaces a hydrogen atom from another brominated compound forming additional brominated compounds, e.g., bromochloro-aniline, bromodichloroaniline, etc. (Hwang et al., 1988). 

If the crystals of 1 are exposed to bromine vapor, addition to the C=C double bond occurs without difficulty, as the molecules can anisotropically migrate along the cleavage plane and the quantitatively obtained trans adduct does not include large amounts of bromine. The gas-solid addition of 2 is more complicated. The initially formed crystalline adduct keeps large quantities of additional bromine and eliminates HBr upon standing and in solution by forming lactones. Thus, mixtures of products arise because consecutive reactions... 

A mixture consisting of the step 2 product (37 g) and 800 ml trimethyl phosphate were charged into a flask and treated with iodine (10.6 g) and the dropwise addition of bromine (19 g) dissolved in 70 ml trimethyl phosphate. After stirring for 4 hours additional bromine (9.5 g) dissolved in 35 ml of trimethyl phosphate was added and the mixture stirred overnight. The reaction liquid was then poured into water, extracted with chloroform, and washed with aqueous solutions of sodium thiosulfate and brine. The solution was then dried, concentrated, the residue purified by silica gel chromatography using cyclohexane/toluene, 20 1, respectively, and... 

Such an octahedron could not be synthesised with L20 in contrast to the tetrahedron, because the additional bromine atoms would point towards each other at unacceptably short distances at each of the corners. The only way to connect these larger triangles as faces of a capsule together is to form a trigonal... 

For efficient allylic bromination, a large concentration of bromine must be avoided because bromine can also add to the double bond (Chapter 8). A-Bromosuccimnude (NBS) is often used as the bromine source in free-radical brominations because it combines with the HBr side product to regenerate a constant low concentration of bromine. No additional bromine is needed because most samples of NBS contain traces of Br2 to initiate the reaction. 

What all flame retardants have in common is that they start to decompose when heated. A critical factor in the selection of a flame retardant is therefore its thermal stability with respect to that of the polymer. The ideal situation is when the flame retardant decomposes at about 50 % below the combustion temperature of the polymer. This is the case with most organic bromine compounds and most synthetic polymers [1]. In addition, brominated flame retardants are economically feasible, and they have little effect on the flexibility of the base compounds [16]. Because of the advantages mentioned above, the commercial use of brominated compounds is attractive. 

We ve already seen several methods for preparing alkyl halides, including the reactions of HX and X2 with alkenes in electrophilic addition reactions (Sections 6.8 and 7.2). The hydrogen halides HCl, HBr, and HI react with alkenes by a polar mechanism to give the product of Markovnikov addition. Bromine and chlorine yield trans 3,2 dihalogenated addition products. 

Complementary to the work on benzoxazoles, Wyeth investigated the prospects of 7-substituted benzofurans [81]. Due to the structural similarity between benzoxazoles and benzofurans it is not much of a surprise that the 7-substituted benzofurans showed high ERp selectivity. ERP affinity was also quite comparable to the corresponding benzofurans. Best results were obtained with 7-acetonitril analog 52, which showed 80-fold selectivity for ERp. Incorporation of an additional bromine at the 4-position (53) resulted in improved ERp affinity and ERP selectivity. 

Olefin additions Bromine azide. Bromine chloride. Bromine (chlorine) dipyridine nitrate. N-Bromoacetamine. N-Bromoacetamide-DMSO-Water. N-Bromoacetamide-Hydrogen fluoride. n-Butyllithium. Dichloroketene. Dichloromethyl 2-chloromethyl ether. N,N-Dichlorourethane. Dichlorovinylene carbonate. Difluoramine. Ethyl azidoformate. Ethyl bromoacetate. Iodine azide. Iodine isocyanate. Iodine nitrate, lodobenzene dichloride. 1-lodoheptafluoropropane. Mercuric acetate. Nitrosyl chloride. Nitrosyl fluoride. Nitryl iodide. Rhodium trichloride. Silver fluoride. 

Addition of fluorine to a C=C bond is different from that of the other halogens in one important respect the heat of reaction exceeds the dissociation energy of an aliphatic C-C bond (80 kcl/mole) quite appreciably. Addition and substitution reactions of fluorine are so exothermic that most organic substances burn or explode if brought into direct contact without special arrangements.15 Addition of F2 to olefins has no preparative importance 48 in the aromatic series addition and substitution result simultaneously. In electrophilic addition, i.e., in most cases, chlorine reacts faster than bromine with olefins, but in nucleophilic addition bromine reacts faster than chlorine.16... 

Some) Additives Brominated flame retardants Plastics and textiles... 

The likelihood that a halogenated solvent will undergo hydrolysis depends in part on the number of halogen substituents. More halogen substituents on a compound will decrease the chance for hydrolysis reactions to occur,and will therefore decrease the rate of the reaction. In addition, bromine substituents are more susceptible to hydrolysis than chlo-... 

Brominated PS is combined with antimony trioxide as a flame retardant [70]. In addition, brominated polyCphenylene ether) has been used. Other flame retardants are tetrabromocyclooctane, tetrabro-movinylcyclohexene, or bis-(allyl ether) tetrabromo-bisphenol A. Eor the latter flame retardants, dicumyl peroxide is added as a synergist [71] and the additives are used together with blowing agents. 

It was demonstrated that a complexation of trans-stilbene with cyclodextrin led to a decrease in stereoselectivity of additive bromination and to a significant yield of DL-stilbene dibromide in contrast to the formation of meso-stilbene dibromide in nonpolar solvents [98]. The authors suggested that this reversal of stereoselectivity was attributed to the polar environment provided by the secondary hydroxyl groups of... 

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