Chlorothalonil
From Wikipedia, the free encyclopedia
| Chlorothalonil | |
|---|---|
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| IUPAC name | 2,4,5,6-tetrachloro- 1,3-benzenedicarbonitrile |
| Other names | Bravo Daconil tetrachloroisophthalonitrile |
| Identifiers | |
| CAS number | [1897-45-6] |
| RTECS number | NT2600000 |
| SMILES | N#CC1=C(Cl)C(C#N)=C(Cl)C(Cl)=C1Cl |
| Properties | |
| Molecular formula | C8Cl4N2 |
| Molar mass | 265.91 g mol−1 |
| Appearance | white crystalline solid |
| Density | 1.8 g cm−3, solid |
| Melting point |
250 °C |
| Boiling point |
350 °C (760 mmHg) |
| Solubility in water | 0.06 g/100 ml |
| log P | 2.88-3.86 |
| Related compounds | |
| Related organochlorides | hexachlorobenzene dichlorobenzene chlorobenzene |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references |
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Chlorothalonil, also known as tetrachloroisophthalonitrile, is a broad spectrum, non-systemic fungicide. 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 is available, it was the third most used fungicide in the US, behind only sulfur and copper, with some 12 million lbs used in agricultural alone that year.[1] Including non-agricultural uses, the EPA estimates that on average almost 15 million lbs were used in annually from 1990-1996.[2]
Contents |
[edit] Uses
In the US, chlorothalonil is used predominantly on peanuts, potatoes, and tomatoes. It is also used on golf courses and lawns and as an additive in some paints.[2]
[edit] Health effects
According to the United States Environmental Protection Agency, chlorothalonil is a Category I "severe" eye irritant. It is not considered to be acutely toxic by ingestion (its oral LD50 is greater than 10,000 mg/kg), but is toxic when inhaled. In animal tests, long term chlorothalonil exposure resulted in kidney damage. Chlorothalonil is a class B2 "probable carcinogen", based on observations of cancers and tumors of the kidneys and forestomach in laborotory animals fed diets containing chlorothalonil.[2]
Chlorothalonil is highly toxic to fish and aquatic invertabrates, but not toxic to birds.[3]
[edit] Environmental contamination
Chlorothalonil has been detected in ambient air in Minnesota and Prince Edward Island. In both cases, the contamination is presumed to have come potato farms.[4][5]
The main breakdown product of chlorothalonil is SDS-3701 (4-hydroxy-2,5,6-trichloroisophthalonitrile). It has been shown to be 30 times more acutley toxic than chlorothalonil and more persistent in the environment.[6] Laboratory experiments have shown that it can thin the eggshells of birds, but there is no evidence that this is happening in the environment.[2]
[edit] Chemistry
Chlorothalonil can by produced by the direct chlorination of isophthalonitrile or by treating tetrachloroisophthaloyl amide with phosphoryl chloride. It breaks down under basic conditions but is stable in neutral and acidic media.[3] Technical chlorothalonil contains traces of dioxins and hexachlorobenzene,[2] a persistent organic pollutant banned under the Stockholm Convention.
[edit] References
- ^ PESTICIDE USE IN U.S. CROP PRODUCTION: 1997 National Center for Food and Agricultural Policy, 1997.
- ^ a b c d e Reregistration Eligibility Decision for chlorothalonil, US EPA, 1999.
- ^ a b Environmental Health Criteria 183, World Health Organization, 1996.
- ^ Pesticides and Air Pollution in Minnesota: The Frequency of Detection of Chlorothalonil, a Fungicide Used on Potatoes. Pesticide Action Newtork North America, Oct 2007.
- ^ White, Louise M & et al., “Ambient air concentrations of pesticides used in potato cultivation in Prince Edward Island, Canada.”, Pest Manag Sci 62 (2): 126-136, <http://www3.interscience.wiley.com/cgi-bin/abstract/112168257/ABSTRACT>
- ^ Cox, Caroline, “Fungicide Factsheet: Chlorothalonil”, Journal of Pesticide Reform 17 (4): 14-20, <http://www.pesticide.org/chlorothalonil.pdf>
