Phenol 2,6-dibromo

Reagent /PhOH 2,6-dibromo- phenol 2,4,6-tribromo- phenol 2-bromo- phenol 2,4-dibromo- phenol 4-bromo- phenol ... 

A. G., and Askaialiev, M., Some reactions of 1055. propargyl ethers of 2,4-dibromo-phenol, Zh. 

Preferably, however, the crude hydroxy sulfonic acids are halogenated in nitrobenzene-sulfuric acid. This affords yields of about 70% of 2,6-dichloro- or 2,6-dibromo-phenol, 72% of o-chlorophenol, or 46.5% of 0-bromophenol.450... 

Needles from EtOH. M.p. 228°. Sol. EtOH, EtgO. Spar. sol. cold HjO. PeCIj — violet col. Soda lime or liot BaO —2 4-dibromo-phenol. 

The other important diol which finds wide application in synthesis of flame retardant epoxy thermosets is 4,4 -isopropylidene bis(2,6-dibromo-phenol) (tetrabromobisphenol-A,TBPA).The primary use of TBPA is as a reactive flame retardant in epoxy resin-based circuit boards and in electronic enclosures made of polycarbonate-acrylonitrile, butadiene-styrene, etc. Hexafluorobisphenol-A (bisphenol-AF, hexafluoroisopropylidene diphenol) has also been used for the synthesis of fluorinated epoxy resin aiming at the anticorrosion coatings market for industrial vessels and pipes. The key disadvantages of fluorinated epoxies are their relatively high costs and low Tg, which limit their commercialisation. Thus utilisation of such diols in vegetable oil-based epoxy resins may result in similar performance. 

Preparation by reaction of acetic anhydride on 2,4-dibromo-phenol with aluminium chloride in nitrobenzene at 120° (41%) [1813,1814]. 

As shown in Figure 17.5, it was evident that the composition of liquid products changed obviously with reaction temperature. At 300 °C (shown in Tables 17.2-17.4), liquid products still contained some bromides, such as 2-bromophenol, 2,6-dibromo-phenol, and 2-methyl-4-isopropyl-bromobenzene, which indicated that brominated... 

One 1-ml aliquot is added to 1.0 ml of freshly-distilled 1,2-dibromo-ethane (bp 132°C) in an oven-dried flask which contains a static atmosphere of nitrogen or argon. After the resulting solution has been allowed to stand at 25°C for 5 min, it Is diluted with 10 rat of water and titrated for base content (residual base) to a phenolphthalein endpoint with standard 0.100 M hydrochloric acid. The second 1-mL aliquot is added cautiously to 10 ml of water and then titrated for base content (total base) to a phenol phthalein endpoint with standard aqueous 0.100 M hydrochloric acid. The methyllithium concentration is the difference between the total base and residual base concentrations.2 Alternatively, the methynithiura concentration may be determined by titration with a standard solution of sec-butyl alcohol employing 2,2 -bipyridyl as an indicator. 

To enhance flame retardancy without use of additives, 2,2-bis-(3,5-dibromo-4-hydroxyphenyl)propane (tetrabromobis-phenol A) has been used in copolymers with bis-phenol A. 

Regioselective bromination of phenols gave 2-bromo-, 4-bromo-, 2,6-dibromo-, 2,4-dibromo, 2-bromo-6-substituted, 4-bromo-2-substituted and 2,4-dibromo-6-substitutgd phenols, respectively. Especially, 2-bromo-, 2,6-dibromo- and 2-bromo-6-substituted phenols which were prepared via long steps, were obtained in NBS-amine (primary and secondary) system in high yields under ordinary conditions. The scope and their mechanisms were discussed. 

With 3-methylphenol (meto-cresol), around 8 % of dibromo products result when one equivalent of brominating agent is used, and this rises to 23 % of dibromo products on attempted monobromination of 3,5-dimethylphenol with 1 molar equivalent of resin. Nevertheless, the good yields of products obtained from the mono-substituted phenols tried demonstrate that this is a powerful new synthetic method for the organic chemist. 

Halogenated phenols, particularly 2-bromo-, 2,4-dibromo-, and 2,4,6-tribromophenol, have been identified in automotive emissions and are the products of thermal reactions involving the dibromoethane fuel additive (Muller and Buser 1986). It could therefore no longer be assumed that such compounds are exclusively the products of biosynthesis by marine algae. 

Desulfitobacterium chlororespirans can use ortho-substituted phenols as electron acceptors for anaerobic growth, and is able to debrominate 2,6-dibromo-4-cyanophenol (Bromoxynil) and 2,6-dibromo-4-carboxyphenol. In contrast, 2,6-diiodo-4-cyanophenol (loxynil) was deiodinated only in the presence of 3-chloro-4-hydroxybenzoate (Cupples et al. 2005). 

Sulfur-containing samples show colored spots when sprayed with 2,6-dibromo-quinone-4-chlorimide Gibbs reagent). For preparation, 2 g of this compound is dissolved in 100 ml of acetic acid or ethanol. Heating to 110°C is necessary to give a reaction. This reagent also creates colored zones when samples contain phenols. For reactions with phenols, only the less-reactive 2,6-dichloroquinone-4-chlorimide can be used under the same conditions. 

Water emissions from paper production softeners (BPA), other phenolic compounds (NPE, APE), other surfactants (LAS), biocides (benzothiazoler, dibromo compounds), wood extractions (terpenoids, resin acids) and more... 

Patents of Dow Chemicals first described 9,9-diaryl-substituted PF homopolymers 204 and 205 by Yamamoto polymerization of the corresponding 2,7-dibromo monomers [272], although the methods for monomer preparation were not described. For unsubstituted fluorenone, a convenient method for its conversion into 9,9-(4-hydroxyphenyl)-[307-309] and 9,9-(4-alkoxyphenyl)fluorenes [310] was reported previously, which included condensation of fluorenone with phenol or its ethers in acidic conditions (dry HC1 [308,309] or H2SO4 [307,311]) in the presence of (3-mcrcaptopropionic or mercaptoacetic acids. Both polymers 204 and 205 showed similar Mn 21,000 with PDI of 1.48 and 1.75, respectively, and spectral data typical for PF (205 Aabs = 389 (r 50,000 //(mol cm) APL = 417, 439, and 473 mn (THF)) (Chart 2.48). 

All of the sulfone diols were able to form oligomers in the second step of the reaction sequence, the Ullmann ether synthesis. As with the synthesis of the mono(bromophenoxy)phenol products, two methods were used to form the dibromo materials. Method A used pyridine, potassium carbonate and cuprous iodide, while Method B employed collidine and cuprous oxide with the dibromobenzene and higher molecular weight diol (IV). The major difference between the syntheses of the mono(bromophenoxy)phenols described earlier and these lies in the stoichiometry of the reactions. In order to... 

UN 2810, see Benzyl alcohol, Bromodichloromethane, Dibromochloromethane, Glycidol, p-Propiolactone UN 2811, see 4-Aminobiphenyl,Benzo[a]anthracene, Benzo[a]pyrene, Benzo[e]pyrene, p-Dimethylaminoazobenzene, Indole UN 2821, see Phenol UN 2831, see 1,1,1-Trichloroethane UN 2842, see Nitroethane UN 2872, see l,2-Dibromo-3-chloropropane UN 2874, see Furfuryl alcohol UN 2976, see CiS-Chlordane, frans-Chlordane UN 2995, see Chlordane UN 2996, see Chlordane UN 3077, see Acenaphthene, Acenaphthylene,... 

White sponge, Dysidea sp. (Fig. 10.5), has been observed to overgrow members of the family Poritidae at Okinawa Island. Extracts from this sponge have been shown to contain brominated diphenyl ethers, which show potent cytotoxicity against P388 cells. Two known compounds, S -dibromo -p /l -dibromophenoxy) and 3,6-dibromo-2-(4 -dibromo-phenoxy)phenol (Fu and Schmitz, 1996 Fu et al., 1995 Fig. 10.6), were... 

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