Everything about Organochloride totally explained
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Two representations
of the organochloride
chloroform. |
An
organochloride,
organochlorine,
chlorocarbon, or
chlorinated solvent 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. These chemicals are typically
nonaqueous and are usually denser than
water due to the presence of heavy chlorine atoms.
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 relatively
non-polar; they're therefore immiscible with water and effective in cleaning applications such as
degreasing and
dry cleaning.
Many organochlorides have significant biological activities, and some can be toxic. For example, many powerful and effective
insecticides are organochlorides. Common examples include
DDT,
dicofol,
heptachlor,
endosulfan,
chlordane,
mirex, and
pentachlorophenol. These can be either
hydrophilic or
hydrophobic.
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).
Natural presence
Although halogenated organic compounds are relatively rare in nature compared to non-halogenated organic compounds, many organochlorides have been isolated from natural sources ranging from bacteria to humans. 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. Organochlorides, including
dioxins, are produced in the high temperature environment of forest fires, and dioxins have been found in the preserved ashes of lightning-ignited fires that predate synthetic dioxins. In addition, a variety of a simple chlorinated hydrocarbons including dichloromethane, chloroform, and
carbon tetrachloride have been isolated from marine algae. A majority of the
chloromethane in the environement is produced naturally by biological decomposition, forest fires, and volcanoes. The natural organochloride
epibatidine, an alkaloid isolated from tree frogs, has potent
analgesic effects and has stimulated research into new pain medication.
Toxicity
Some types of organochlorides have significant toxicity to plants or 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. For example, mid-twentieth century overuse of DDT, which accumulates in animals because the body is unable to break down or dispose of them, resulted in the severe decline of some bird populations. In addition, chlorinated solvents, when not handled and disposed of properly, present problems with groundwater pollution because they break down very slowly in the environment. Some highly reactive organochlorides such as
phosgene have even been used as
chemical warfare agents.
However, the presence of chlorine in an organic compound doesn't in any way ensure toxicity. Many organochlorides are safe enough for consumption in foods and medicines. For example, peas and broad beans contain the natural chlorinated plant hormone
4-chloroindole-3-acetic acid (4-Cl-IAA); and the sweetener
sucralose (Splenda) is widely used in diet products. As of 2004, there were at least 165 organochlorides approved worldwide for use as pharmaceutical drugs, including the antihistamine
loratadine (Claritin), the antidepressant
sertraline (Zoloft), the anti-epileptic
lamotrigine (Lamictal), and the inhalation anesthetic
isoflurane.
With her influential 1962 book
Silent Spring,
Rachel Carson brought the issue of organochloride toxicity to public awareness. While many countries have phased out the use of some types of organochlorides (such as the US ban on DDT as a result of Carson's work), 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.
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