Halogen compounds functions

The role of antimony oxide is not entirely understood. On its own it is a rather weak fire retardant although it appears to function by all of the mechanisms listed above. It is, however, synergistic with phosphorus and halogen compounds and consequently widely used. Other oxides are sometimes used as alternatives or partial replacements for antimony oxide. These include titanium dioxide, zinc oxide and molybdenic oxide. Zinc borate has also been used. 

Foucaud A (1983) Positive halogen compounds. In Pattai S, Rappoport Z (eds) The chemistry of functional groups, supplement D. Wiley, New York, pp 441-480... 

Although the primary utility of active halogen compounds is to modify sulfhydryl groups in proteins or other molecules, the reaction is not totally specific. Iodoacetyl (and bromoacetyl) derivatives can react with a number of functional groups within proteins the sulfhydryl group of cysteine, both imidazolyl side chain nitrogens of histidine, the thioether of methionine, and... 

Transport Rates. The amount of halogenated compounds in the hexane layer increased linearly with time for up to 12 h for all compounds transported. For many compounds the relationship remained linear for at least 24 h and then it started to level off. This increase, expressed as a transport rate in ug/h was a linear function of the amount added to the flask (Table I). 

The presence of halogen additives substantially increases the tendency of all fuels to soot under diffusion flame conditions [69], The presence of H atoms increases the soot pyrolysis rate because the abstraction reaction of H + RH is much faster than R + RH, where R is a hydrocarbon radical. Halogenated compounds added to fuels generate halogen atoms (X) at modest temperatures. The important point is that X + RH abstraction is faster than H + RH, so that the halogen functions as a homogeneous catalyst through the system... 

The cyanohydrin not only adds an additional C at the site of the C==0 but also introduces two new functional groups, OH and CN. which can be used to introduce other functional groups. The OH can be used to form an alkene (C=C), an ether (—RO), or a halogen compound (C—X) the C N can be reduced to an amine (CHjNHj), be hydrolyzed to a carboxyl (COOH) group, or react with Grignard reagents if the OH is protected. 

Vinylidene fluoride is taken up rapidly via the pulmonary route in rats, but at equilibrium the mean concentration (by volume) in rats was only 23% of that in the gaseous phase. Metabolism proceeded very slowly and was saturable at exposure concentrations of about 260 mg/m Its maximum rate was 1% that of vinyl chloride and less than 20% that of vinyl fluoride there has been a report of an increase in the urinary excretion of fluoride in exposed rats. No alkylating intermediate was demonstrated after passage through a mouse-liver microsomal system. However, vinylidene fluoride inhibits mixed-function oxidase activity in vitro and, like similar halogenated compounds that are transformed to reactive metabolites, it alters rat intermediary metabolism, leading to acetone exhalation (lARC, 1986). 

Apart from lengthening the chain by one carbon atom, this reaction provides a compound with two readily modified functional groups. Many other halogen compounds offer a more complex picture. Radical-derived products are sometimes obtained, but in other cases a heterolytic mechanism must operate, for example to give a methyl ether when naphthylmethyl iodides are irradiated in methanol (5.651. 

Because of anomalies present when halogenated compounds were eluted. Lovelock proposed the theory that electronegative specie functionally present in an organic molecule, could capture an electron to form a negatively charged species ... 

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