Organohalogens halogen compounds

More recently, based on the results of an extensive series of small scale degradation studies, two additional mechanisms for the volatilization of antimony from antimony oxide/organohalogen flame retardant systems have been proposed (23,24). Of these two proposed mechanisms, [4] and [5], [4] does not involve HX formation at all and [5] suggests an important role for the direct interaction of the polymer substrate with the metal oxide prior to its reaction with the halogen compound. 

Organohalogenated compounds, referred to here as halocarbons, are widely distributed in the environment (1-4). Some industrially produced compounds, such as polychlorinated biphenyls and DDT [l,l -(2,2,2-tri-chloroethylidene)bis[4-chlorobenzene]] are biologically refractory and toxic pollutants of water and land. Volatile synthetic halocarbons such as chlo-rofluorocarbons (CFCs), a significant component of the greenhouse gases in the atmosphere, cause depletion of the ozone layer (5). Halogenated compounds also are produced naturally. The widespread occurrence of natural... 

As recently as 1970, only about 30 naturally occurring organohalogen compounds were known. It was simply assumed that chloroform, halogenated phenols, chlorinated aromatic compounds called PCBs, and other such substances found in the environment were industrial pollutants. Now, only a third of a century later, the situation js quite different. More than 5000 organohalogen compounds have been found to occur naturally, and tens of thousands more surely exist. From a simple compound like chloromethane to an extremely complex one like vancomycin, a remarkably diverse range of organohalogen compounds exists in plants, bacteria, and animals. Many even have valuable physiological activity. Vancomycin, for instance, is a powerful antibiotic produced by the bacterium Amycolatopsis orientalis and used clinically to treat methicillin-resistant Staphylococcus aureus (MRSA). 

Tiernan TO, Solch JG, Garrett JG, et al. 1990. Concerted analytical method for determination of various halogenated and related bioaccumulating compounds in fish and sediments. Organohalogen Compounds, vol. 2. ORCOEP. pp225-228. 

Table 7.4 Typical mass fractions, w, of the halogenated products found in the combustion of organohalogen compounds [42,64]...

In another paper, adsorbable organohalogen compounds (AOX) were adsorbed on activated charcoal, which, after treatment to remove inorganic halogens, was pyrolyzed at about 1000°C and the HC1 formed was dried online and determined by titration with electrogenerated silver ion [66]. The computer... 

I he general description organohalogen refers to compounds with covalent carbon-halogen bonding. Substances such as bromomethane, CH3Br, and chlo-roethene, CH2=CHC1, are examples of organohalogen compounds, whereas... 

There is wide diversity in the nature of organohalogen compounds but, of necessity, we have restricted this chapter to alkyl, cycloalkyl, alkenyl, alkynyl, and aryl halides. Some of the chemistry of the carbon-halogen bonds already will be familiar to you because it involves the addition, substitution, and elimination reactions discussed in previous chapters. To some extent, we will amplify these reactions and consider nucleophilic substitution by what are called the addition-elimination and elimination-addition mechanisms. Subsequently, we will discuss the formation of carbon-metal bonds from carbon-halogen bonds. The latter type of reaction is of special value because compounds that have carbon-metal bonds are potent reagents for the formation of carbon-carbon bonds, as we will show later in this chapter. 

One of the more important reactions of organohalogen compounds is the formation of organometallic compounds by replacement of the halogen by a metal atom. Carbon is positive in carbon-halogen bonds and becomes negative in carbon-metal bonds, and therefore carbon is considered to be reduced in formation of an organometallic compound (see Section 11-1) ... 

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