Halogen requirement

Additive flame-retardant compounds include brominated epoxy resins, chlorinated hydrocarbons, decabromodiphenyl ether, and pentabromodiphenyl ether. Where transparency is not important, antimony oxide can be used as a synergist to reduce the amount of halogen required. 

The halogens required for this reaction may be generated in situ, for example, through oxidation of hydrogen halides by copper(II) acetate12. Organic vicinal dibromides release their bromine atoms to tellurium13,14. 

One further point requires clarification. We have said that an E ct of 33 kcal is too great for the reaction between iodine atoms and methane to proceed at a significant rate yet the initial step in each of these halogenations requires an even... 

Still, on a comparative basis, reactivity is limited. Magic acid is, after all, one of the strongest acids known halogenation requires heat or light combustion needs a flame or spark to get it started. 

Tetraalkyl and tetraaryl germanium compounds possess monomeric structures with tetrahedrally sited germanium. They are thermally stable and tend to be chemically inert halogenation requires a catalyst (equations 18.49 and 18.50). Chlorides can be obtained from the corresponding bromides or iodides by halogen exchange (equation 18.51). The presence of halo-substituents increases reactivity (e.g. equation 18.52) and makes the halo-derivatives synthetically more useful than R4Ge compounds. 

Chlorination and bromination in the side chain of alkylaromatic compounds requires exclusion of the catalysts of ionic halogenation, i.e., above all of metal salts. Thus it is recommended to add substances that form stable complexes with metal salts, e.g., ethylenedinitrilotetraacetic acid (EDTA).417 Side-chain halogenation requires conditions under which radicals can be formed, illumination (100-200 household lamps or UV), high temperatures, and addition of radical formers. Discoloration occurring during side-chain chlorination, which inhibits light absorption, can be avoided by adding 0.1-5% of benzamide.418... 

The greater reactivity of pyridine-1-oxide towards nitration as compared to pyridine is noteworthy. It proceeds smoothly in nitrating acid, via the free base and the a-complex 77, yielding 4-nitropyridine-l-oxide 78 (see p 274). Other Sg reactions (sulfonation, halogenation) require drastic conditions. 

Oxyhalides have a halide ion substituted for an oxygen ion in the perovskite structure. As with the oxynitrides, addition of a halogen requires charge compensation, typically via a change in the nominal cation valence. Oxyhalides with a formula ABOjF are generally approximated as ionic compounds, so that... 

Rotary kilns used for de-halogenation require a capacity of the order of 0.6 m per tonne of raw fume processed per day, and typical kilns are of the order of 2.0 to 2.5 m OD and 20 to 30 m in length. Kiln slope is around 4° and refractory lining is typically 150 to 250 mm thick. Examples of commercial... 

Quantity of halogen required to impart flame retardancy upon a clear epoxide casting... 

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