Degree of bromination

Octabromodiphenyl Oxide. Octabromodiphenyl oxide [32536-52-0] (OBDPO) is prepared by bromination of diphenyl oxide. The degree of bromination is controlled either through stoichiometry (34) or through control of the reaction kinetics (35). The melting poiat and the composition of the commercial products vary somewhat. OBDPO is used primarily ia ABS resias where it offers a good balance of physical properties. Poor uv stabiUty is the primary drawback and use ia ABS is being supplanted by other brominated flame retardants, primarily TBBPA. 

Permeability is also as reported in Barrier, one Barrier being equal to 1X10 1°P. It can be seen from Table I that no change either in permeability for C02 or C02/CH4 selectivity was obtained when the degree of bromination for PPO is low (6.5 mole%). However, at higher levels of bromination, there were increases in both permeability for C02 and C02/CH4 selectivity. The maximum effects (an increase of 2.47 times for C02 permeability and 1.45 times for C02/CH4 selectivity to that of PPO) were reached at 100% substitution degree of the aromatic ring. 

For the decabromodiphenyl oxide (DBDPO) pyrolysis reactions, two different procedures were used to synthesize the series of brominated diphenyl oxides and dibenozofurans employed as the relative retention time standards AlBr3/Br2 in ethylene dibromide and Fe° (metal)/Br2 in tetrachloroethylene. The rate of the initial bromination steps in the former reaction was so rapid that only the higher degree of bromination adducts could be isolated. The rate of the Fe°/Br2 reaction was found to be much slower, especially during the initial stages, and these reactions yielded a broader range of relative retention time reference peaks. 

The most significant characteristic of these data, as compared to that from Class X and II, was the overall increase in component peak areas for the lower degree of bromination furans (4 to 6 bromines accounting for 12-20% as compared to =2% for Class I and a maximum of 14% for Class II) and ethers (6 and 7 bromines accouting for 7-29% as compared to =1% for Class I and a maximum for 4% for Class II). ... 

Brominated bisphenol A compounds with the lowest degree of bromination showed the highest estrogenic potencies (EC50 value of 0.5 pM for 3-monobromobi-sphenol A). 

Ecobichon DJ, Hansell MM, Safe S. 1979. Isomerically pure bromobiphenyl congeners and hepatic mono-oxygenase activities in the rat Influence of position and degree of bromination. Toxicol Appl Pharmacol 47 341-352. 

Brominated indigo with a lower degree of bromination is also commercially available. 

Reaction of phenols with BTMABr3 or TBABr3 in a methanol/methylene chloride solvent mixture results in a step-by-step bromination. The degree of bromination depends solely on the molar ratio of reagent to substrate (equation 64)522. With the first mole of reagent / -bromophenol is obtained, followed by 2,4- dibromophenol and, finally, 2,4,6-tribromophenol. The role of methanol in these systems is apparently the in situ formation of methyl hypobromite. The same selectivity is, however, found in chloroform523. 

The three analysed risk assessments are contemporary and have all been performed by die same European Union member stales (the UK and France except for the risk assessment for Penta that the UK was the sole rapporteur for). They furthermore cover three substances that are chemically closely related, representing three brominated diphenyl ethers, used as flame retardants, with different degrees of bromination. 

In general, PBBs show an unusual chemical stability and resistance to acids, bases, heat, reduction and oxidation. PBBs are chemically comparable to the PCBs. However, chlorine atoms have a stronger association to polybiphenyl than bromine atoms [2]. Unlike PCBs, the reactivity of PBBs has not been well studied and documented in the literature [11]. Like PCBs, their chemical stability is dependent, in part, on the degree of bromination and the specific substitution patterns [12]. 

The bromination of poly-DCH is of interest because the degree of bromine uptake can be controlled, by choice of experimental conditions, between 3 and 8 Br atoms per polymer repeat unit and because a crystal-to-crystal transformation is observed. Scheme 1 summarizes the reactions of liquid bromine with poly-DCH. Interaction of poly-DCH crystals with dense vapors of bromine or cyanogen bromide for months did not lead to detectable weight gain. By contrast, DCH monomer (2a), which has a crystal structure similar to the polymer (6), readily reacts with bromine vapor to give an eunor-phous material which has gainbd ca 12 Br atoms per molecule. 

Interestingly, the dibrominated compound could be methylated by derivatisation with trimethylsulphonium hydroxid (TMSH) forming the corresponding methylether. The mass spectra are presented in Fig. 7. In contrast, the monobrominated phenol remained unaffected as the result of less acidity due to the lower degree of bromine substitution. 

Figure 3.54 The 75 MHz NMR spectrum of the aromatic region of a 57 mol% brominated poly(2,6-dimethyl-l,4-phenylene oxide) polymer. Assignments are shown for peaks used in determining the degree of bromination. (From Williams et al., used with permission.)...

However, within a series of monovalent cations with increasing ionic radius, such as Li+,K+,Cs+, the permeability decreases in this order for nonpolar gases. The same is true for earth alkaline cations in the series Mg +,Mg +,Ca +. Therefore, it is concluded that both the size of the cation plays a role in increasing the void volume, and the change in polarity is another factor for the performance. In brominated PPE, the permeability of gases increases with the degree of bromination. °... 

Affi ossman, S., O Neill, S.A., Stamm, M. Topography and surface composition of thin films of blends of polystyrene with brominated polystyrenes Effects of varying the degree of bromination and annealing. Macromolecules 31(18), 6280-6288 (1998)... 

Poly (ethylene terephthalate) (PET) was first introduced as a synthetic fibre when flameretarded by grafting with bromostyrene. Later PET and poly(butylene terephthalate) (PBT) emerged as engineering plastics, so that their more effective flame-retardance became of crucial importance. Diphenyls and diphenyl oxides at different degrees of bromination as well as brominated polymeric flame-retardants have been proposed (e.g. PBB-PA, Dead Sea PO 64 P, Great Lakes.) ... 

Some studies have been carried out comparing the capabilities of the two MS approaches (El and NCI) for the PBDE determinations. Comparison of detection limits for PBDEs clearly indicates that NCI offers better sensitivity than does El NCI-MS gave detection limits between 30 fg and 1.72 pg, whereas EI-MS gave detection limits between 0.53 pg and 32.09 pg. The main advantage of EI-MS is that it provides better structural information. No structural information on the degree of bromination was obtained by NCI. The mass spectra of all PBDEs were dominated by the molecular ion [Br] and did not show any molecular ion. However, El provided better structural information, giving the molecular ions and the sequential losses of bromine atoms. Moreover, the use of EI-MS allowed the use of an isotopic dilution method for quantification, making the analysis more reliable at trace levels. 

PBDEs with a low degree of bromination such as those contained in commercial pentaBDE are likely to undergo LRT... 

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