An organochlorine compound, chlorocarbon or chlorinated hydrocarbon, is an organic substance containing at least one covalently bonded chlorine atom that affects the chemical behavior of a molecule. The class of chloralkanes (alkanes with one or more hydrogen atoms substituted by chlorine) gives common examples. The wide structural diversity and various chemical properties of organochlorine compounds lead to a wide range of names and applications. Organochlorides are very useful substances in many applications, but some of them pose a serious environmental problem.
Impact on properties
Chlorination alters the physical properties of hydrocarbons in several ways. Compounds are generally more dense than water, due to the higher atomic weight of chlorine compared to hydrogen. Aliphatic organochlorides are alkylating agents because chloride is a leaving group.
Determination of organochlorine compounds
Many of these compounds have been isolated from natural sources, from bacteria to humans. Chlorinated organic compounds are found in almost every class of biomolecules, including alkaloids, terpenes, amino acids, flavonoids, steroids and fatty acids. Organochlorides, including dioxins, are formed in the high-temperature environment of forest fires, and dioxins were found in the preserved ash of fires caused by lightning, which preceded synthetic dioxins.
In addition, various simple chlorinated hydrocarbons, including dichloromethane, chloroform and carbon tetrachloride, have been isolated from algae. Most of the chloromethane in the environment is formed naturally through biodegradation, forest fires and volcanoes. Organochlorine compounds in oil are also widely known (according to GOST R 52247-2004).
Epibatidine
Natural organochlorine epibatidine, an alkaloid isolated from tree frogs, has a strong analgesic effect and stimulates the study of new painkillers. Frogs receive epibatidine through food, and then isolate it on the skin. Potential food sources include bugs, ants, ticks, and flies.
Alkanes
Alkanes and arylalkanes can be chlorinated under free radical conditions with ultraviolet radiation. However, the degree of chlorination is difficult to control. Aryl chlorides can be prepared by hardening Friedel-Crafts using chlorine and an acid Lewis catalyst. Methods for the determination of organochlorine compounds include the use of this catalyst. Other methods are also mentioned in the article.
The haloform reaction using chlorine and sodium hydroxide is also capable of generating alkyl halides from methyl ketones and related compounds. Chloroform was previously produced in this way.
Chlorine adds alkenes and alkynes to the plural bonds, giving di- or tetrachloro compounds.
Alkyl chlorides
Alkyl chlorides are universal building blocks in organic chemistry. Although alkyl bromides and iodides are more reactive, alkyl chlorides are less expensive and more affordable. Alkyl chlorides are easily attacked by nucleophiles.
Heating the alkyl halides with sodium hydroxide or water gives alcohols. Reaction with alkoxides or aroxides gives esters in the synthesis of Williamson ester; reactions with thiols give thioethers. Alkyl chlorides readily react with amines to form substituted amines. Alkyl chlorides are replaced by softer halides, such as iodide, in the Finkelstein reaction.
A reaction with other pseudo-halides such as azide, cyanide and thiocyanate is also possible. In the presence of a strong base, alkyl chlorides undergo dehydrohalogenation to form alkenes or alkynes.
Alkyl chlorides react with magnesium to form Grignard reagents, converting the electrophilic compound to nucleophilic. The Wurz reaction, in a reducing manner, combines two alkyl halides with sodium.
Application
The largest use of organochlorine chemistry is the production of vinyl chloride. The annual production volume in 1985 was about 13 billion kilograms, almost all of which were converted to polyvinyl chloride (PVC). The determination of organochlorine compounds (according to GOST) is a process that cannot be completed without special standardized equipment.
Most low molecular weight chlorinated hydrocarbons, such as chloroform, dichloromethane, dichloroethane and trichloroethane, are useful solvents. These solvents tend to be relatively non-polar; therefore, they do not mix with water and are effective in cleaning, such as degreasing and dry cleaning. This purification also relates to methods for the determination of organochlorine compounds (oil and other substances are very rich in these compounds).
The most important is dichloromethane, which is mainly used as a solvent. Chloromethane is a precursor to chlorosilanes and silicones. Historically significant, but smaller in scale is chloroform, mainly the precursor of chlorodifluoromethane (CHClF2) and tetrafluoroethene, which is used in the manufacture of Teflon.
The two main groups of organochlorine insecticides are DDT-type substances and chlorinated alicyclic solutions. Their mechanism of action is slightly different from organochlorine compounds in oil.
DDT-like compounds
DDT-like substances affect the peripheral nervous system. In the sodium channel of the axon, they prevent the closure of the gate after activation and depolarization of the membrane. Sodium ions leak through the nerve membrane and create a destabilizing negative "postpotential" with increased nerve excitability. This leakage causes repeated discharges in the neuron either spontaneously or after one stimulus.
Chlorinated cyclodienes include aldrin, dieldrin, endrin, heptachlor, chlordane and endosulfan. Duration of exposure from 2 to 8 hours leads to a decrease in the activity of the central nervous system (CNS), followed by increased excitability, tremor, and then attacks. The mechanism of action is the binding of insecticides to the GABA site in the ionophore complex of gamma-aminobutyric acid chloride (GABA), which prevents the entry of chloride into the nerve.
Other examples include dicofol, mirex, kepon, and pentachlorophenol. They can be either hydrophilic or hydrophobic, depending on their molecular structure.
Biphenyls
Polychlorinated biphenyls (PCBs) were once widely used electrical insulators and coolants. Their use, as a rule, was discontinued due to health problems. PCBs have been replaced by polybrominated diphenyl ethers (PBDEs), which cause similar problems with toxicity and bioaccumulation.
Some types of organochlorine compounds have significant toxicity to plants or animals, including humans. Dioxins generated by the burning of organic substances in the presence of chlorine are persistent organic pollutants that are hazardous when released into the environment, like some insecticides (such as DDT).
For example, DDT, which was widely used to control insects in the mid-20th century, also accumulates in food chains, like its metabolites, DDE and DDD, and causes reproductive problems (such as thinning eggshells) in some bird species. Some compounds of this type, such as sulfur mustard, nitrogen mustard and lewisite, are even used as chemical weapons due to their toxicity.
Intoxication with organochlorine compounds
However, the presence of chlorine in the organic compound does not provide toxicity. Some organochlorides are considered safe enough for food and medicine. For example, peas and beans contain the natural chlorinated plant hormone 4-chloroindole-3-acetic acid and Sucralose sweetener (Splenda) are widely used in diet foods.
As of 2004, at least 165 organochlorides have been approved worldwide for use as pharmaceuticals, including the natural antibiotic vancomycin, the antihistamine loratadine (clarithin), the antidepressant sertraline (zoloft), the antiepileptic lamotrigine (lamictal), and inhaled drugs. isoflurane anesthetic. It is necessary to know these compounds for the determination of organochlorine compounds in oil (according to GOST).
Conclusions of scientists
Rachel Carson introduced the public to the issue of DDT pesticide toxicity in her 1962 book, Silent Spring. Although many types of organochlorine compounds have been discontinued in many countries, such as the U.S. ban on DDT, persistent DDT, PCBs and other organochlorine residues are still found in humans and mammals across the planet many years after production and use were limited.
In the Arctic regions, particularly high levels are found in marine mammals. These chemicals are concentrated in mammals and are even found in human breast milk. In some species of marine mammals, especially those that produce milk with a high fat content, in males, as a rule, much higher levels, as females lower their concentration, transferring substances to offspring as a result of lactation. Also, these substances can be in oil, which is important to consider when determining organochlorine compounds in oil (according to GOST). This usually applies to pesticides, although it can also apply to any compound of this type.
Organochlorine pesticides can be classified by their molecular structures. Cyclopentadiene pesticides are aliphatic cyclic structures resulting from the Diels-Alder Pentachlorocyclopentadiene reactions and include chlordane, nonachlor, heptachlor, heptachlor epoxide, dieldrin, aldrin, endrin, mirex and kepon. Other subclasses of organochlorine pesticides are the DDT family and hexachlorocyclohexane isomers. All these pesticides have low solubility and volatility and are resistant to environmental degradation processes. Their toxicity and persistence in the environment have led to their limitation or suspension for most uses in the United States.
Pesticides
Organochlorine pesticides are very effective in killing pests, especially insects. But many of these chemicals are negatively perceived by environmental activists and consumers because of one well-known and now banned organochlorine pesticide: dichlorodiphenyltrichoretan, better known as DDT.
Organochlorine pesticides are chemicals with carbon, chlorine and hydrogen. As explained by the US Fisheries and Wildlife Service, chlorine-carbon bonds are especially strong, which prevents these chemicals from quickly breaking down or dissolving in water. The chemical also attracts fat and accumulates in the adipose tissue of animals that consume it.
The durability of the chemical composition of organochlorine pesticides is one of the reasons why it is as effective as an insecticide and potentially harmful - it can protect crops for a long time, but can also remain in the body of the animal.
Along with DDT, the US Environmental Protection Agency has banned the use of other organochlorine pesticides such as aldrin, dieldrin, heptachlor, mirex, chlordecone, and chlordane. Many organochlorine pesticides are similarly banned in Europe, but in both of these regions, organochlorine chemicals are still active in a number of pest control products at home, in the garden, and in the environment, according to the EPA. Organochlorine pesticides are also extremely popular in developing countries around the world for agricultural use.
Regardless of whether you are researching farmland to make sure it is still filled with summer organochlorine pesticides, or inspecting water for organochlorine compounds, testing is the best way to find out if these chemicals are near you. EPA methods 8250A and 8270B can be used to test these chemicals. The 8250A can test waste, soil, and water, while the 8270B uses gas chromatography / mass spectrometry (GC / MS).
Although organochlorine pesticides are best known for damaging the ability of some birds to lay healthy eggs, it is known that these chemicals negatively affect people who consume or inhale pesticides. Accidental inhalation or ingestion of contaminated fish or animal tissue is the most likely way to swallow organochlorine pesticides. To confirm that someone has signs of organochlorine poisoning, blood or urine is usually sent to a university or government agency that uses GC / MS to check for chemical compounds.
Signs of Poisoning
Warning signs of organochlorine pesticide toxicity include convulsions, hallucinations, coughing, skin rashes, vomiting, abdominal pain, headaches, confusion, and possibly respiratory failure according to Matthew Wong, Ph.D., Ph.D., and Beth Israel Deaconess Medical Center, Medscape . Although many of these pesticides are banned in the United States and Europe, their use in other parts of the world and their storage in parts of the United States and Europe create situations where organochlorine poisoning is still possible.
Organochlorine pesticides include a large number of persistent chemicals that are both effective and carry significant risk worldwide.
Although halogenated organic compounds are relatively rare in nature compared to non-halogenated ones, many such compounds have been isolated from natural sources, from bacteria to humans. There are examples of naturally occurring chlorine compounds found in almost every class of biomolecules, including alkaloids, terpenes, amino acids, flavonoids, steroids and fatty acids.
Organochlorides, including dioxins, are formed in the high-temperature environment of forest fires, and dioxins were found in the preserved ash of fires caused by lightning, which preceded synthetic dioxins. In addition, various simple chlorinated hydrocarbons, including dichloromethane, chloroform and carbon tetrachloride, have been isolated from algae.
Most of the chloromethane in the environment is formed naturally through biodegradation, forest fires and volcanoes. Natural organochlorine epibatidine, an alkaloid isolated from tree frogs, has a strong analgesic effect and stimulates the study of new painkillers.
Dioxins
Some types of organochlorine compounds have significant toxicity to plants or animals, including humans. Dioxins from the burning of organic substances in the presence of chlorine, and some insecticides such as DDT, are persistent organic pollutants that pose a threat to the environment. For example, the excessive use of DDT in the mid-twentieth century, which accumulates in animals, has led to a serious decline in the populations of some birds. Chlorinated solvents, if handled and disposed of improperly, cause problems with groundwater pollution.
Some organochlorides, such as phosgene, have even been used as chemical warfare agents. Some of the artificially created and toxic organochlorides, such as DDT, will accumulate in the body with every exposure, which will ultimately lead to a lethal amount because the body cannot destroy them or get rid of them. However, the presence of chlorine in the organic compound in no way provides toxicity. Many organochlorine compounds are safe enough for consumption in food and medicine.
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