Paraquat (a trivial name; ) or N , N ? - dimethyl-4,4? - bipyridinium dichloride (systematic name) is an organic compound with the chemical formula [Cl 7 N) 2 sub> 2 . These are classified as viologen, a redox-active heterocyclic family of similar structures. Paraquat is produced by Chevron. This salt is one of the most widely used herbicides. It acts quickly and is not selective, killing the green plant tissue when touching. It is also toxic to humans and animals due to redox activity, which results in superoxide anions. It has been linked to the development of Parkinson's disease. This name is derived from the para position of the quaternized nitrogen . Paraquat may be in the form of a salt with chloride or other anions; the amount of substance is sometimes expressed by the mass of the cation alone (paraquat cation, paraquat ion).
Video Paraquat
Produksi
Pyridine is combined with treatment with sodium in ammonia followed by oxidation. Results 4.4? -bipyridine is then methylated with chloromethane to give the title compound:
Maps Paraquat
Use of herbicide
Although first synthesized in 1882, the nature of the paraquat herbicide was not recognized until 1955. Paraquat was first produced and sold by ICI in early 1962, and is today among the most commonly used herbicides.
The European Union approved the use of paraquats in 2004 but Sweden, backed by Denmark, Austria and Finland, appealed this decision. In 2007, the court nullified the guidelines allowing paraquats as an active crop protection substance stating that the 2004 decision was wrong in finding that there was no indication of paraquat-related neurotoxicity and that studies of the association between paraquat and Parkinson's disease should have been done. considered.
Paraquat is classified as a non-selective contact herbicide. The key characteristics that differentiate it from other agents used in plant protection products are:
- Kill a wide variety of weeds and broadleaf weeds and endless weeds.
- Act very fast.
- It rains quickly within minutes of the app.
- Some are inactive when in contact with the ground.
These properties cause the paraquat to be used in the development of agriculture without tillage. Current research into landless farming using mulch technique as a substitute for herbicide application produces good results.
In the United States, paraquat is available primarily as a solution in various strengths. This is classified as "limited use", which means that it can be used by licensed applicators only. In the EU, paraquats have been banned since 2007. A small group of countries, including India and Guatemala and supported by producers, have blocked the paraquat list as dangerous chemicals for the purpose of the Rotterdam Convention.
Reactivity and action mode
Paraquat adalah oksidan yang mengganggu transfer elektron, suatu proses yang umum untuk semua kehidupan. Penambahan satu elektron memberikan kation radikal:
- [MV] 2 e - [MV]
Kation radikal juga rentan terhadap reduksi lebih lanjut ke [MV] netral 0 :
- [MV] e - [MV] 0
As herbicides, paraquat acts by inhibiting photosynthesis. In plants exposed to light, it receives electrons from photosystem I (more specifically ferredoxin, which is presented with electrons from PS I) and transfers them to oxygen molecules. In this way, a destructive reactive oxygen species is produced. In forming this reactive oxygen species, the paraquat oxidized form is regenerated, and again available to drive electrons from photosystem I to restart the cycle.
Paraquat is often used in science to catalyze the formation of reactive oxygen species (ROS), more specifically, superoxide free radicals. Paraquats will undergo redox cycles in vivo, reduced by electron donors such as NADPH, before being oxidized by electron receptors such as dioxygen to produce superoxide, a large ROS.
Weed resistance management
Problems with herbicide-resistant weeds can be overcome by applying herbicides with different mode of action, along with cultural methods such as crop rotation, in an integrated weed management system (IWM). Paraquat, with its distinctive mode of action, is one of several chemical options that can be used to prevent and mitigate the problem with weeds that have become resistant to the widely used non-selective glyphosate herbicides.
One example is the "double knock" system used in Australia. Before planting the weeds, sprayed with glyphosate first, then followed seven to ten days later with paraquat herbicide. Although twice as expensive as using a single glyphosate spray, the "Double Knock" system is an important resistance management strategy that many farmers rely on. However, herbicide resistance has been seen for both herbicides in Western Australia.
A computer simulation shows that with annual turnover between glyphosate and paraquat, only one field in five would be expected to have annual glyphosate-resistant ryegrass (Lolium rigidum) after 30 years, compared with nearly 90% of the fields sprayed with glyphosate. The "Double Doubles" regime with paraquat cleansing after glyphosate is predicted to make all fields free of glyphosate resistant ryegrass for at least 30 years.
Toxicity
Pure paraquat, when ingested, is highly toxic to mammals, including humans, potentially causing acute respiratory distress syndrome (ARDS). Although there is no special antidote, fuller soil or activated charcoal is an effective treatment if taken on time. There are several cases that successfully use cyclophosphamide to treat paraquat poisoning. Death can occur up to 30 days after consumption. The dissolved paraquat used to spray is less toxic; thus, the greatest risk of accidental toxicity is during mixing and loading of paraquats to be used.
In studies of acute toxicity using laboratory animals, paraquat has been shown to be highly toxic by inhalation routes and has been placed in Toxicity Category I (highest of four levels) for acute inhalation effects. However, the EPA has determined that the particles used in agricultural practices (400-800 m) are well beyond the inhalable range and therefore the inhalation toxicity is not a dangerous toxicological endpoint. Paraquat is toxic (Category II) by oral route and is quite toxic (Category III) by dermal route. Paraquat will cause moderate to severe eye irritation and minimal skin irritation, and has been placed in Toxicity Category II and IV (slightly toxic) respectively for this effect.
The alveolar lung epithelial cells selectively concentrate the paraquat. Even once gulping, immediately spitting out, can cause death from the fibrous tissue that develops in the lungs, leading to asphyxia.
One of the characters in the famous British public information film Apaches (1977) died within hours of accidentally ingesting a small amount; the paraquat in the film is contained in a container similar to a whiskey bottle.
According to the Centers for Disease Control, swallowing paraquat causes symptoms such as liver, lung, heart, and kidney failure within days to weeks that can cause death up to 30 days after consumption. Those who suffer from large exposures are unlikely to survive. Chronic exposure can cause lung damage, kidney failure, heart failure, and oesophageal stricture. Death by accident and the suicide of paraquat ingestion is relatively common. For example, there are more than 5,000 deaths in China due to paraquat poisoning each year. Long-term exposure to paraquat is likely to cause lung and eye damage, but reproductive/fertility damage is not found by the United States Environmental Protection Agency (EPA) in their review.
"Paraquat pot"
During the late 1970s, a controversial program sponsored by the US government sprayed paraquats in marijuana fields in Mexico. After Mexico's efforts to eradicate marijuana and poppy fields in 1975, the United States government helped by sending helicopters and other technological aids. Helicopters are used to spray paraquat and 2,4-D herbicides in the fields; marijuana contaminated with these substances began to appear in the US market, leading to debate about the program. Perhaps in an effort to prevent people from using marijuana, representatives of the program warn that spraying makes plants insecure to smoke.
Whether the injury occurred due to inhaling the contaminated marijuana uncertainty. A 1995 study found that "no lung or other injury to cannabis users has ever been associated with paraquat contamination". Also, the US Environmental Protection Agency's guidance states: "... the toxic effects caused by this mechanism are extremely rare or absent.Most of the paraquats contaminating marijuana are fanned as smoking becomes dipyridyl, which is a leaf-burning product of its own (including cannabis ) and presents a bit of a toxic hazard. "
In a study by Imperial Chemical Industries, rats who inhaled paraquat showed a development of squamous metaplasia in their respiratory tract after several weeks. The study was included in a report given to the Department of Foreign Affairs by Miter Corporation. The US Public Health Service stated that "this study should not be used to calculate safe doses of paraquat in humans."
Use suicide and kill
Most (93 percent) of casualties due to paraquat poisoning are suicides, occurring mainly in developing countries. For example, in Samoa from 1979-2001, 70 percent of suicides were caused by paraquat poisoning. Trinidad and Tobago is best known for the suicide incidents involving the use of Gramoxone (the commercial name of paraquat). In southern Trinidad, particularly in Penal, Debe from 1996-1997, 76 percent of suicides were perpetrated by paraquats, 96 percent of which involved excessive alcohol consumption such as rum. Fashion Celebrity Isabella Blow committed suicide using paraquat in 2007. Paraquat is widely used as a suicide agent in third world countries because it is widely available at low cost. Furthermore, a low toxic dose (10 mL or 2 teaspoons is enough to kill). Campaigns exist to control or even prohibit paraquat, and there is a movement to limit its availability by requiring user education and locking paraquat stores.
Indiscriminate killing of paraquat, which occurred in Japan in 1985, was carried out using paraquat as a poison.
Paraquat, as Gramoxone weedkiller, was used in England in 1981 by Susan Barber to poison her husband's pie sauce Michael. He was convicted of murder in November 1982, defending the whole that he had no intention of killing him.
Parkinson's disease
In 2011, a US National Institutes of Health study showed a link between the use of paraquat and Parkinson's disease in agricultural workers. A paper author says that paraquat increases the production of certain oxygen derivatives that can harm cellular structures, and that people who use paraquat, or other pesticides with similar mechanisms of action, are more likely to develop Parkinson's. Paraquat-induced toxicity in mice has also been linked to Parkinson's neurological degenerative mechanisms. A study by the Buck Institute for Research on Aging showed a link between paraquat and iron exposure in infants and mid-life Parkinson's in laboratory mice. A 2013 meta-analysis published in Neurology found that "paraquat exposure... was associated with about twice the increased risk" of Parkinson's disease.
Paraquat is structurally similar to MPP, a rapidly acting inducer of Parkinson's disease in the primate brain. MPP chloride is sold under the trade name Cyperquat.
Paraquat also induces oxidative stress in invertebrates such as Drosophila melanogaster . Feedflies fed an early-onset of death and a significant increase in superoxide dismutase activity.
Paraquat in developing countries
Paraquat was promoted in developing countries since the 1960s and is classified as quite toxic. It is responsible for the deaths of thousands of people around the world. Paraquat is banned in many countries: Austria, Denmark, Hungary, Republic of Korea, Sweden and Switzerland, etc. Nevertheless the Permanent Commission of the European Commission on the Animal Food and Veterinary Chain approve the use of paraquat in EU countries, although such disputes are some of them. US-EPA classifies paraquat as a restricted pesticide. Despite ongoing international campaigns for global bans, cheap paraquats and hence popular continue to be unrestricted in most developing countries.
References
Further reading
- Slade, P. (1966). "Paraquat's Fate is Applied to Plants". Weed Research . 6 (2): 158-167. doi: 10.1111/j.1365-3180.1966.tb00876.x.
- Smith, S. N.; Lyon, A. J. E.; Sahid, Ismail BIN (1976). "The Breakdown of Paraquat and Diquat by Soil Fungi". New Phytologist . 77 (3): 735-740. doi: 10.1111/j.1469-8137.1976.tb04668.x.
External links
- "Paradox Product". Sinon do Brasil.
- "Stop Paraquat". ErklÃÆ'¤rung von Bern. Archived from the original in 2007-06-08.
- "The Paraquat Information Center". Syngenta Crop Protection AG. Ã ,
- "NIOSH Pocket Guide to Chemical Hazards". Centers for Disease Control and Prevention.
- Paraquat in Pesticide Properties DataBase (PPDB)
- Paraquat dichloride in Pesticide Properties DataBase (PPDB)
Source of the article : Wikipedia
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