Organochloride
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| Two representations of the organochloride chloroform. |
An organochloride, organochlorine or chlorocarbon, is an organic compound containing at least one covalently bonded chlorine atom. Their wide structural variety and divergent chemical properties lead to a broad range of uses.
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[edit] Applications
The simplest form of organochlorides are chlorinated hydrocarbons. These consist of simple hydrocarbons in which one or more hydrogen atoms have been replaced with chlorine. Most low molecular weight chlorinated hydrocarbons such as chloroform, dichloromethane, dichloroethene, and trichloroethane are useful as solvents. These solvents tend to be immiscible with water. Additionally, because organochlorides are polar solvents, they dissolve a wide variety of chemical compounds.
Many organochlorides have significant biological activities. For example, many powerful and effective insecticides are organochlorides. Common examples include DDT, dicofol, heptachlor, endosulfan, chlordane, mirex, and pentachlorophenol.
Polychlorinated biphenyls (PCBs) were once commonly used electrical insulators and heat transfer agents. Their use has generally been phased out due to health concerns.
Chlorinated alkenes are useful monomers used in the preparation of a variety of materials. For example, vinyl chloride is polymerized to form the plastic polyvinyl chloride (PVC).
[edit] Natural abundance
Although halogenated chemical compounds are relatively rare in nature compared to non-halogenated compounds, many organochlorides have been isolated from natural sources ranging from bacteria to humans.[1] There are examples of natural chlorine-containing compounds found in nearly every class of biomolecules including alkaloids, terpenes, amino acids, flavonoids, steroids, and fatty acids.[1][2] In addition, a variety of a simple chlorinated hydrocarbons including dichloromethane, chloroform, and carbon tetrachloride have been isolated from marine algae.[3] An interesting example of a natural organochloride is epibatidine, an alkaloid isolated from tree frogs, which has potent analgesic effects and has stimulated research into new pain medication. Despite these examples, the amount of organochlorides of biological origin in the environment are small compared to those of anthropogenic origin.
[edit] Toxicity
Many organochlorides have significant toxicity to animals, including humans. Dioxins, produced when organic matter is burned in the presence of chlorine, and some insecticides such as DDT are persistent organic pollutants which pose dangers to the environment. Chlorinated solvents, when not handled and disposed of properly, present problems with groundwater pollution. Some organochlorides such as phosgene have even been used as chemical warfare agents. However, the presence of chlorine in an organic compound does not in any way ensure toxicity. Many organochlorides are safe enough for consumption in foods and medicines such as loratadine (Claritin), sertraline (Zoloft), lamotrigine (Lamictal), and the sweetener sucralose (Splenda).
Rachel Carson was the American scientist that brought attention of the issue of organochloride toxicity to public awareness with her 1962 book Silent Spring. While many countries have phased out the use of some organochlorides, persistent organochlorides continue to be observed in humans and mammals across the planet at potentially dangerous levels many years after production and use have been limited. In Arctic areas, particularly high levels are found in marine mammals. These chemicals especially impact mammals, and are even found in human breast milk. Males typically have far higher levels, as females reduce their concentration by transfer to their offspring through breast feeding.[4]
[edit] See also
[edit] References
- ^ a b Gordon W. Gribble, "Naturally Occurring Organohalogen Compounds", Acc. Chem. Res., 31 (3), 141 -152, 1998.
- ^ Kjeld C. Engvild, "Chlorine-Containing Natural Compounds in Higher Plants", Phytochemistry, Vol. 25, No. 4, 7891-791, 1986.
- ^ Gribble, G. W. , "Naturally occurring organohalogen compounds - A comprehensive survey", Progress in the Chemistry of Organic Natural Products (1996), 68, 1-423.
- ^ Marine Mammal Medicine, 2001, Dierauf & Gulland
