Phenols brominated

Brominated Phenols. Tribromophenol [75-80-9] and dibromophenol [615-58-7] are both prepared through bromination of phenol. These are not actually used as reactive flame retardants, but rather as starting materials for other flame retardants such as BTBPE [37853-59-1] and epoxy oligomers. 

Consequently the bromine adduct was obtained in high yield (83 %). Using NBS and a catalytic amount of the amine, the ratio of the ort/io-brominated phenols was remarkably raised. 2-Allylphenol and o-cresol were considerably orr/io-brominated by NBS even without the amine. In NBS-amine system dibromides as by-products were obtained slightly and any p jra-bromide and bromine adduct in the case of 2-allylphenol were not detected. 

It is generally supported that the bromination with NBS proceeded by a radical (ref. 11) or an ionic mechanism via bromine molecule. For instance, the former was suggested in benzylic and allylic bromination with NBS for Whol-Ziegler reaction (ref. 12). Calo et al. (ref. 5) accounted NBS brominated phenol by the latter mechanism. 

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. 

Tribromophenol and other simple brominated phenols (No. 66, 2005) Tributyltin oxide (No. 14, 1999)... 

Method B TMBA-Br, (see Table 2.22) is added to the phenol (4.62 mmol) in CH2C12 (50 ml) and MeOH (20 ml). The mixture is stirred for 1 h at room temperature until the orange colour fades. The solvent is evaporated and the residue is extracted with Et20 (4 x 40 ml). The dried (MgS04) extracts are evaporated to yield the brominated phenol. 

Kuramochi, H., Maeda, K., and Kawamoto, K. Water solubility and partitioning behavior of brominated phenols. Environ. Toxicol Chem., 23(6) 1386-1393, 2004. 

Watanabe, 1., Kashimoto, T., andTatsukawa, R. Brominated phenol production from the chlorination of wastewater containing bromide ions. Bull. Environ. Contam. Toxicol, 33(4) 395-399, 1984. 

In general, aromatic halogenation proceeds to give the para product. Jallal M. Gnaim of the The Triangle Regional R D Center, Kfar-Qari, Israel, has developed (Tetrahedron Lett. 2004,45, 8471) a procedure that selectively converts phenols such as 1 into the ortho chlorinated product 2. Meta substitution is even more elusive. William R. Roush, now at Scripps Florida, prepared (J. Org. Chem. 2004,69,4906) the valuable meta brominated phenol 4 by perbromination followed by selective reduction. 

Jacquesy et al.556 have succeeded in preparing mefa-bromophenols from phenols using the Br2-HF-SbF5 system. The orf/zo-protonated phenol or alkyl phenyl ether, which is in equilibrium with the neutral precursor, reacts with the reactive Br+ in the HF-SbF5 medium, leading to only mefa-brominated phenols (Scheme 5.59). The ring protonated phenols are unreactive toward electrophilic bromine in the superacid... 

The toxic Japanese gastropod Turbo marmorata contains the two toxins, turbotoxins A (1983) and B (1984), isolated as bis-trifluoroacetates (1824, 1825). The turbotoxins A and B show LD99 = 1.0 and 4.0 mg kg 1 in mice. The simple iodinated ammonium salt 1985 is also found in this animal (1826). The red alga Halopytis incurvus contains the simple brominated phenols 1986 and 1987, which were isolated as the methyl esters and methyl ethers (1827). These presumed degradation products of tyrosine are related to earlier reported brominated metabolites (1). 

Ahn Y-B, Rhee S-K, Fennell DE, Kerkhof LJ, Hentschel U, Haggblom MM (2003) Reductive Dehalogenation of Brominated Phenolic Compounds by Microorganisms Associated with the Marine SpongeAplysina aerophoba. Appl Environ Microbiol 69 4159... 

Incubation in soils showed that polybrominated biphenyls were resistant to degradation, but were apparently not taken up by plants or leached into groundwater [261]. Commercial formulations of brominated aromatic flame retardants had variable composition some contained highly brominated phenols, but no evidence of contamination with dibenzodioxins and dibenzofurans was found [198]. 

The cyclopropanone ring is susceptible to attack by electrophilic reagents other than acids, e.g. bromine, phenol, acid chlorides. Most of these reactions have been observed in cyclopropanone acetals and all proceed by attack at C2 or Cg in a manner analogous to path b, Scheme 28. As shown in Table 18, esters are usually obtained but, under special bro-mination conditions, 1,1-dialkoxycarbonium halides are formed.109) These salts lose ROBr upon warming to — 30 °C to give the expected esters. 

Pronuciferine (1) has been synthesized by photocyclization of the brominated phenol (2).9a The light-induced rearrangement of proaporphines yields aporphines that are substituted at C-9 or at both C-8 and C-9.5 This topic is further discussed below, under the sections on aporphines and aporphine dimers. The known alkaloid N-methylcrotsparine has been found in Pachygone ovata.9b... 

Figure 2. SEM view of wood fibers impregnated with brominated phenol-formaldehyde resin. The line trace indicates bromine concentration in the wood...

A very different solution, and one suitable even for the selective production of HBr in the presence of chlorine, without any catalyst, is the treatment of the pyrolysis oils with molten polypropylene [13, 63, 56, 57, 59], Polypropylene acts within a temperature range of 310-350°C as a hydrogen donor. HBr is evolving from the brominated phenols and substituted phenols are formed in the case of the decomposition of flame retardants such as tetrabromobisphenol A (Figme 20.8). Together with HBr small brominated aliphatics are formed. Those can be converted to HBr together with all noncondensable compounds in a final oxidative cleaning. 

Oxidative coupling was used for the synthesis of some stabilizers having properties of AO or FR. Products of oxidation of 4,4 -isopropylidenebis(2-methyl-6-tert-butylphenol with pota ium ferricyanide [151] or of 4,4 -thiobis(2-rcr/-butyl-5-methylphenol) with oxygen in the presence of copper salts [152] (118) were tested as AO. Thermostable fireproofing additives containing 1 to 4 bromine atoms on a phenolic moiety and designed for the stabilization of thermoplastics, e.g. 119, were prepared by oxidative coupling of brominated phenols [153]. 

Other acids can be used to promote chlorination or bromination. N-Bromosuccinimide and HBF4 can be used to brominate phenols with high pnra-selectivity, as can pyridinium bromide perbromide, and NBS in acetic acid with ultrasound is effective. The use of NBS with a catalytic amount of HCl has also been reported. Both NCS and NBS with aqueous BF3 gave the respective chloride or bromide. Note that NBS in an ionic liquid gave the brominated aromatic. Bromine on silica gel gave good yields of the brominated aromatic compound. HBr with hydrogen peroxide... 

Bisphenol A Brominated bisphenol A Brominated phenol 2,2 -bis(4-Hydroxyphenyl)propane 80-05-7... 

Epoxy resin Poly-(diallyl-phthalate) ABS PC-ABS blend Brominated bisphenol A Dechlorane Plus Octabromodiphenyl oxide Brominated phenol, triphenyl phosphate 0.5 mg sample at 950°C DB-5 fused silica capillary, 30 m x 0.25 mm i.d., 1.0-pm film 40°C for 4 min, ramp at 10°C/min to 320°C, hold for 18 min MS (El, 15-650 mass range) Injector T = 300°C detector T = 300°C 30/1 injection spUt [49]a,e... 

Bromination. Phenols and anilines undergo monobromination at room temperature in good yields. 

Use Brominating phenols and addition to double bonds mono- and polybromination of ketones, including aliphatic, alicyclic, steroid, and amino carbonyls. Micro or semimicro quantitative analysis. 

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