Aromatic compounds brominations

The chlorine content of the fly ash is 4.9 %, the bromine content 0.065 %. A series of brominated aromatic compounds has been adsorbed on this fly ash and treated for 1 h. with air at 300°C. The extraction and analysis yield mixed brominated/chlorinated as well as completely chlorinated products. This is shown for 5 aromatic bromine compounds in Table 2. 

The studies on the effect of brominated aromatic compounds on the activity of ALA-D and ALA-S provide an introduction to the examination of porphyrogenic effect of these compounds. Disturbance in these enzymes as well as in URO decarboxylase activity according to some authors, might function as an introduction in development of liver porphyrias. 

Chlorine and Bromine. Aromatic compounds can be brominated or chlorinated by treatment with bromine or chlorine in the presence of a catalyst, most often iron. However, the real catalyst is not the iron itself, but the ferric bromide or ferric chloride formed in small amounts from the reaction... 

Bromide analysis, of water, 26 41 Bromide ions, in development solution, 79 205-206 Bromides, 4 319-330 thorium, 24 763 titanium, 25 54 tungsten, 25 379 uranium, 25 439 Bromimide, 4 299, 319 Brominated additive flame retardants, 77 461-468, 471-473t Brominated Anthanthrone Orange, pigment for plastics, 7 367t Brominated aromatic compounds, 7 7 459 Brominated bisphenol A-based epoxy resins, 70 366... 

Kohli J, Safe S. 1976. The metabolism of brominated aromatic compounds. Chemosphere 6(6) 433-437. 

Lonza Ltd in Visp, Switzerland, developed at the beginning of the 1990s a process for the halogen exchange of a brominated aromatic compound with butyl lithium followed by the C—C coupling to a ketone [44]. 

Buser HR (1976), Anal. Chem. 58 2913-2919.. .Selective detection of brominated aromatic compounds using gas chromatography/negative chemical ionization mass spectrometry"... 

The most common halogen-based flame retardants used in styrenic polymers are listed in Table 29.1 [23]. The majority of these are brominated aromatic compounds used to flame retard HIPS and ABS. As mentioned in Section 4, roughly 10 wt% of bromine is required to pass UL 94 V-0 requirements. Antimony trioxide is also used in combination with these brominated compounds. 

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... 

Although the Birckenbach-Goubeau-Waters methods of nuclear bromina-tion and iodination are applied under very similar conditions, most, though not all, of the other processes for nuclear iodination differ from the usual methods of chlorinating and brominating aromatic compounds. Since iodination by elemental iodine is reversible (g),... 

Bromination. Bromine complexed to polymeric pyridine has been used to brominate aromatic compounds. 

Aromatic bromination. Addition of KBr generates positive bromine species that can brominate aromatic compounds. 

The two flame retardant materials contained two different heavily brominated aromatic compounds. A simple FTIR pyrolysis cell was used for the evaluation. On decomposition, the PBTP polymers gave off mainly water, carbon dioxide, butadiene, THF and PBTP oligomers. The flame retardants increased marginally the polymer decomposition temperature. The merits of the test equipment are discussed. Results were consistent with previous TGA results. 7 refs. 

Blend of brominated aromatic compound with triaryl phosphate... 

Of the halogenated organics, brominated aromatic compounds are the most extensively used. Decabromodiphenyl oxide or Saytex BT-93 is approved, but poly-(dibromophenylene oxide) is specifically recommended for polyamides. Brominated epoxy resins are also suitable flame-retardants for polyamides. The synergetic partner additive is antimony trioxide in most cases. 

A broad range of halogenated flame retarding compoimds can be used in conjunction with antimony trioxide, typically chlorinated paraffins and chlorinated cycloaliphatic compoimds, brominated aromatic compounds and brominated phosphates. However, the major application for antimony trioxide in terms of consumption is in flexible PVC, where the chlorine available from the polymer is sufficient to provide the desired level of flame retardancy. 

It was found that oligomeric brominated aromatic compounds containing s-triazine rings (s-Triazine Compounds) prepared by polycondensation of cyanuric chloride, tetra-bromobisphenol A and tribromophenol were excellent flame retardants. 

Based on the above mentioned stand points, cyanuric chloride was chosen as an s-triazine ring source. Brominated phenols were chosen as mono- and bifunctional brominated aromatic compounds to be polycondensated with... 

Flame-retardant grades of PBT usually consist of synergistic mixtures of antimony trioxide with various halogenated (brominated) aromatic compounds. A typical recipe for PBT might be 10 wt% decabromodiphenyl oxide and 5 wt% antimony oxide. Recently the trend has been to use polymeric or oligomeric brominated additives. A typical additive is an end-capped polycarbonate derived from tetrabromobisphenol-A [94334-64-2] another is a mixture of epoxy oligomers derived from the diglycidyl ether of tetrabromobisphenol-A [68928-70-1]. The brominated polystyrenes (Zoc. cit.) have only limited usefulness in PBT as they have a low melt compatibility (107). 

The use of pyridinium dichlorobromate (PyHBrCl2) gives 2-bromothiophene in 74% yield (Scheme 67) [102]. The non-nucleophilic base, l,8-diazabicyclo[5.4.0] undec-7-ene (DBU), in combination with HBr and bromine gives a stable complex DBUHBrs that is able to brominate aromatic compounds thus, 2-bromo- and 2,5-dibromothiophenes were obtained in good yields (Scheme 67) [103]. 

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