Names | |
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Preferred IUPAC name 2,4,5,6-Tetrachlorobenzene-1,3-dicarbonitrile | |
Other names 2,4,5,6-Tetrachloroisophthalonitrile Bravo Daconil Tetrachloroisophthalonitrile Celeste Bronco Agronil Aminil | |
Identifiers | |
3D model (JSmol) | |
ChEBI | |
ChEMBL | |
ChemSpider | |
ECHA InfoCard | 100.015.990 |
EC Number |
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KEGG | |
PubChem CID | |
RTECS number |
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UNII | |
UN number | 3276, 2588 |
CompTox Dashboard (EPA) | |
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Properties | |
C8Cl4N2 | |
Molar mass | 265.90 g·mol−1 |
Appearance | white crystalline solid |
Density | 1.8 g cm−3, solid |
Melting point | 250 °C (482 °F; 523 K) |
Boiling point | 350 °C (662 °F; 623 K) (760 mmHg) |
10 mg/100 mL [1] | |
log P | 2.88–3.86 |
Hazards | |
GHS labelling: | |
Danger | |
H317, H318, H330, H335, H351, H410 | |
P201, P202, P260, P261, P271, P272, P273, P280, P281, P284, P302+P352, P304+P340, P305+P351+P338, P308+P313, P310, P312, P320, P321, P333+P313, P363, P391, P403+P233, P405, P501 | |
Related compounds | |
Related nitriles; organochlorides | benzonitrile; hexachlorobenzene, dichlorobenzene, chlorobenzene |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). |
Chlorothalonil (2,4,5,6-tetrachloroisophthalonitrile) is an organic compound mainly used as a broad spectrum, nonsystemic fungicide, with other uses as a wood protectant, pesticide, acaricide, and to control mold, mildew, bacteria, algae. [2] Chlorothalonil-containing products are sold under the names Bravo, Echo, and Daconil. It was first registered for use in the US in 1966. In 1997, the most recent year for which data are available, it was the third most used fungicide in the US, behind only sulfur and copper, with 12 million pounds (5.4 million kilograms) used in agriculture that year. [3] Including nonagricultural uses, the United States Environmental Protection Agency (EPA) estimates, on average, almost 15 million lb (6.8 million kg) were used annually from 1990 to 1996. [2]
In the US, chlorothalonil is used predominantly on peanuts (about 34% of usage), potatoes (about 12%), and tomatoes (about 7%), although the EPA recognizes its use on many other crops. [2] It is also used on golf courses and lawns (about 10%) and as a preservative additive in some paints (about 13%), resins, emulsions, and coatings. [2]
Chlorothalonil is commercially available in many different formulations and delivery methods. It is applied as a dust, dry or water-soluble grains, a wettable powder, a liquid spray, a fog, and a dip. It may be applied by hand, by ground sprayer, or by aircraft. [2]
Chlorothalonil reacts with glutathione giving an glutathione adduct with elimination of HCl. Its mechanism of action is similar to that of trichloromethyl sulfenyl fungicides [4] such as captan and folpet. [5]
According to the EPS, chlorothalonil is a toxicity category I eye irritant, producing severe eye irritation. It is in toxicity category II, "moderately toxic", if inhaled (inhaled LD50 0.094 mg/L in rats.) For skin contact and ingestion, chlorothalonil is rated toxicity category IV, "practically nontoxic", meaning the oral and dermal LD50 is greater than 10,000 mg/kg. [2]
Long-term exposure to chlorothalonil resulted in kidney damage and tumors in animal tests. [2]
Chlorothalonil is a Group 2B "possible human carcinogen" (N.B. : in the Group 2A of International Agency for Research on Cancer IARC are the "probable human carcinogen" substances), based on observations of cancers and tumors of the kidneys and forestomachs in laboratory animals fed diets containing chlorothalonil. [2] To give context, the IARC evaluates Pickled vegetables (traditional Asian) as a Group 2B possible human carcinogen, and night shift work and drinking very hot beverages as Group 2A probable human carcinogen substances.
Chlorothalonil was found to be an important factor in the decline of the honey bee population, by making the bees more vulnerable to the gut parasite Nosema ceranae . [6]
Chlorothalonil is highly toxic to fish and aquatic invertebrates, but not toxic to birds. [7]
At a concentration of 164 μg/L, chlorothalonil was found to kill a species of frog within a 24-hour exposure. [8]
Common chlorothalonil synthesis procedures frequently result in contamination of it with small amounts of hexachlorobenzene (HCB), which is toxic. US regulations limit HCB in commercial production to 0.05% of chlorothalonil. According to the EPA report, "post-application exposure to HCB from chlorothalonil is not expected to be a concern based on the low level of HCB in chlorothalonil. 2,3,7,8-Tetrachlorodibenzodioxin being one of the most potent carcinogens known is also a known contaminant". [2]
Chlorothalonil has been detected in ambient air in Minnesota [9] and Prince Edward Island, [10] as well as in groundwater in Long Island, New York [2] and Florida. [2] In the first three cases, the contamination is presumed to have come from potato farms. It has also been detected in several fish kills in Prince Edward Island. [11]
The main breakdown product of chlorothalonil is hydroxy-2,5,6-trichloro-1,3-dicyanobenzene (SDS-3701). It has been shown to be 30 times more acutely toxic than chlorothalonil and more persistent in the environment. [12] [13] Laboratory experiments have shown it can thin the eggshells of birds, but no evidence supports this happening in the environment. [2]
In 2019, a review of the evidence found that "a high risk to amphibians and fish was identified for all representative uses", and that chlorothalonil breakdown products may cause DNA damage. [14] [15] Around the same time, research indicated chlorothalonil and other fungicides to be the strongest factor in bumblebee population decline. [14]
Syngenta sued to stop communication by Swiss health authorities with the Swiss public regarding the "relevance" of specific metabolites of chlorothalonil that Swiss authorities detected in high concentrations in the groundwater from which hundreds of thousands of Swiss people obtain drinking water. The court banned Swiss health authorities from communicating with the public about the dangers posed by some of the metabolites. [16]
In March 2019, as a result of the previously mentioned research, the European Union banned the use of chlorothalonil [14] dated to take effect May 20, 2020. [17] Switzerland followed in December 2019. [18]
The removal of chlorothalonil and its metabolites is usually achieved by very expensive, technically complex and unecological methods such as reverse osmosis, nano- or microfiltration. In addition, dilution is achieved by mixing with uncontaminated water. However, this only reduces the concentration, the substances still remain in the water. In technologies based on membrane technology, the membranes must be cleaned regularly with chemicals, which is expensive and not ecological.
Recent research results from a Swiss company show very good results for the removal of chlorothalonil and its metabolites. In contrast to the conclusion described in the Eawag fact-sheet, it was also possible to remove the metabolites R471811 and chlorothalonil sulfonic acid from water using a filter material based on activated carbon. The first measurements did not even reach the detection limit. Thus, it was shown that it is possible to completely remove the pesticide residues. [19]
Chlorothalonil can be produced by the direct chlorination of isophthalonitrile or by dehydration of tetrachloroisophthaloyl amide with phosphoryl chloride. [20] It is a white solid. It breaks down under basic conditions, but is stable in neutral and acidic media. [7] Technical grade chlorothalonil contains traces of dioxins and hexachlorobenzene, [2] a persistent organic pollutant banned under the Stockholm Convention.
A biocide is defined in the European legislation as a chemical substance or microorganism intended to destroy, deter, render harmless, or exert a controlling effect on any harmful organism. The US Environmental Protection Agency (EPA) uses a slightly different definition for biocides as "a diverse group of poisonous substances including preservatives, insecticides, disinfectants, and pesticides used for the control of organisms that are harmful to human or animal health or that cause damage to natural or manufactured products". When compared, the two definitions roughly imply the same, although the US EPA definition includes plant protection products and some veterinary medicines.
Bromomethane, commonly known as methyl bromide, is an organobromine compound with formula CH3Br. This colorless, odorless, nonflammable gas is produced both industrially and biologically. It has a tetrahedral shape and it is a recognized ozone-depleting chemical. It was used extensively as a pesticide until being phased out by most countries in the early 2000s.
Lindane, also known as gamma-hexachlorocyclohexane (γ-HCH), gammaxene, Gammallin and benzene hexachloride (BHC), is an organochlorine chemical and an isomer of hexachlorocyclohexane that has been used both as an agricultural insecticide and as a pharmaceutical treatment for lice and scabies.
Carbofuran is a carbamate pesticide, widely used around the world to control insects on a wide variety of field crops, including potatoes, corn and soybeans. It is a systemic insecticide, which means that the plant absorbs it through the roots, and from there the plant distributes it throughout its organs where insecticidal concentrations are attained. Carbofuran also has contact activity against pests. It is one of the most toxic pesticides still in use.
Imidacloprid is a systemic insecticide belonging to a class of chemicals called the neonicotinoids which act on the central nervous system of insects. The chemical works by interfering with the transmission of stimuli in the insect nervous system. Specifically, it causes a blockage of the nicotinergic neuronal pathway. By blocking nicotinic acetylcholine receptors, imidacloprid prevents acetylcholine from transmitting impulses between nerves, resulting in the insect's paralysis and eventual death. It is effective on contact and via stomach action. Because imidacloprid binds much more strongly to insect neuron receptors than to mammal neuron receptors, this insecticide is more toxic to insects than to mammals.
Pentachlorophenol (PCP) is an organochlorine compound used as a pesticide and a disinfectant. First produced in the 1930s, it is marketed under many trade names. It can be found as pure PCP, or as the sodium salt of PCP, the latter of which dissolves easily in water. It can be biodegraded by some bacteria, including Sphingobium chlorophenolicum.
Persistent organic pollutants (POPs) are organic compounds that are resistant to degradation through chemical, biological, and photolytic processes. They are toxic chemicals that adversely affect human health and the environment around the world. Because they can be transported by wind and water, most POPs generated in one country can and do affect people and wildlife far from where they are used and released.
Biomagnification, also known as bioamplification or biological magnification, is the increase in concentration of a substance, e.g a pesticide, in the tissues of organisms at successively higher levels in a food chain. This increase can occur as a result of:
Atrazine is a chlorinated herbicide of the triazine class. It is used to prevent pre-emergence broadleaf weeds in crops such as maize (corn), soybean and sugarcane and on turf, such as golf courses and residential lawns. Atrazine's primary manufacturer is Syngenta and it is one of the most widely used herbicides in the United States, Canadian, and Australian agriculture. Its use was banned in the European Union in 2004, when the EU found groundwater levels exceeding the limits set by regulators, and Syngenta could not show that this could be prevented nor that these levels were safe.
Fipronil is a broad-spectrum insecticide that belongs to the phenylpyrazole chemical family. Fipronil disrupts the insect central nervous system by blocking the ligand-gated ion channel of the GABAA receptor and glutamate-gated chloride (GluCl) channels. This causes hyperexcitation of contaminated insects' nerves and muscles. Fipronil's specificity towards insects is believed to be due to its greater binding affinity for the GABAA receptors of insects than to those of mammals, and for its action on GluCl channels, which do not exist in mammals. As of 2017, there does not appear to be significant resistance among fleas to fipronil.
Hexachlorobenzene, or perchlorobenzene, is an aryl chloride and a six-substituted chlorobenzene with the molecular formula C6Cl6. It is a fungicide formerly used as a seed treatment, especially on wheat to control the fungal disease bunt. It has been banned globally under the Stockholm Convention on Persistent Organic Pollutants.
Methoxychlor is a synthetic organochloride insecticide, now obsolete. Tradenames for methoxychlor include Chemform, Maralate, Methoxo, Methoxcide, Metox, and Moxie.
Acibenzolar-S-methyl is the ISO common name for an organic compound that is used as a fungicide. Unusually, it is not directly toxic to fungi but works by inducing systemic acquired resistance, the natural defence system of plants.
Enilconazole is a fungicide widely used in agriculture, particularly in the growing of citrus fruits. Trade names include Freshgard, Fungaflor, and Nuzone.
Pentachloronitrobenzene, typically abbreviated PCNB, is a registered fungicide formally derived from nitrobenzene. It is either an off-white or yellow solid, depending on its purity, with a musty odor.
This is an index of articles relating to pesticides.
Chlorpropham or CIPC is a plant growth regulator and herbicide used as a sprout suppressant for grass weeds, alfalfa, lima and snap beans, blueberries, cane fruit, carrots, cranberries, ladino clover, garlic, seed grass, onions, spinach, sugar beets, tomatoes, safflower, soybeans, gladioli and woody nursery stock. It is also used to inhibit potato sprouting and for sucker control in tobacco. Chlorpropham is available in emulsifiable concentrate and liquid formulations.
2,4-Dichlorophenoxyacetic acid is an organic compound with the chemical formula Cl2C6H3OCH2CO2H. It is usually referred to by its ISO common name 2,4-D. It is a systemic herbicide that kills most broadleaf weeds by causing uncontrolled growth, but most grasses such as cereals, lawn turf, and grassland are relatively unaffected.
Tetrachlorvinphos is an organophosphate insecticide used to kill fleas and ticks.
Cyproconazole is an agricultural fungicide of the class of azoles, used on cereal crops, coffee, sugar beet, fruit trees and grapes, on sod farms and golf courses and on wood as a preservative. It was introduced to the market by then Sandoz in 1994.