Tefluthrin

Last updated
Tefluthrin
Tefluthrin.svg
tefluthrin (racemic)
Names
Preferred IUPAC name
rac-(2,3,5,6-Tetrafluoro-4-methylphenyl)methyl (1R,3R)-2,2-dimethyl-3-[(1Z)-2-chloro-3,3,3-trifluoroprop-1-en-1-yl]cyclopropane-1-carboxylate
Other names
Tefluthrine
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.124.968 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 616-699-6
KEGG
PubChem CID
UNII
  • InChI=1S/C17H14ClF7O2/c1-6-11(19)13(21)7(14(22)12(6)20)5-27-15(26)10-8(16(10,2)3)4-9(18)17(23,24)25/h4,8,10H,5H2,1-3H3/b9-4-/t8-,10-/m1/s1 Yes check.svgY
    Key: ZFHGXWPMULPQSE-SZGBIDFHSA-N Yes check.svgY
  • InChI=1/C17H14ClF7O2/c1-6-11(19)13(21)7(14(22)12(6)20)5-27-15(26)10-8(16(10,2)3)4-9(18)17(23,24)25/h4,8,10H,5H2,1-3H3/b9-4-/t8-,10-/m1/s1
    Key: ZFHGXWPMULPQSE-SZGBIDFHBO
  • CC1=C(C(=C(C(=C1F)F)COC(=O)[C@@H]2[C@@H](C2(C)C)/C=C(/C(F)(F)F)\Cl)F)F
Properties [1]
C17H14ClF7O2
Molar mass 418.74 g·mol−1
Appearancecolorless solid
Density 1.48 g/mL
Melting point 44.6 °C
Boiling point 156 °C at 1 mmHg
0.02 mg/L in water

>500 g/L in acetone, hexane, toluene

log P 6.4
Hazards [2]
GHS labelling:
GHS-pictogram-skull.svg GHS-pictogram-pollu.svg
Danger
H300, H310, H330, H410
P260, P262, P264, P270, P271, P273, P280, P284, P301+P310, P302+P350, P304+P340, P310, P320, P321, P322, P330, P361, P363, P391, P403+P233, P405, P501
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Tefluthrin is the ISO common name [3] for an organic compound that is used as a pesticide. [1] It is a pyrethroid, a class of synthetic insecticides that mimic the structure and properties of the naturally occurring insecticide pyrethrin which is present in the flowers of Chrysanthemum cinerariifolium . Pyrethroids such as tefluthrin are often preferred as active ingredients in agricultural insecticides because they are more cost-effective and longer acting than natural pyrethrins. [4] It is effective against soil pests because it can move as a vapour without irreversibly binding to soil particles: in this respect it differs from most other pyrethroids. [5]

Contents

Synthesis

Tefluthrin manufacture.svg

Tefluthrin (X=CH3) is manufactured by the esterification of cyhalothrin acid chloride [6] with 4-methyl-2,3,5,6-tetrafluorobenzyl alcohol. [7] The latter was a novel compound when tefluthrin was invented [8] and the choice of routes to it has been discussed. [9]

History

By 1974, a team of Rothamsted Research scientists had discovered three pyrethroids suitable for use in agriculture, namely permethrin, cypermethrin and deltamethrin. [10] These compounds were subsequently licensed by the NRDC, as NRDC 143, 149 and 161 respectively, to companies which could then develop them for sale in defined territories. Imperial Chemical Industries (ICI) obtained licenses to permethrin and cypermethrin but their agreement with the NRDC did not allow worldwide sales. Also, it was clear to ICI's own researchers at Jealott's Hill that future competition in the marketplace might be difficult owing to the greater potency of deltamethrin compared to the other compounds. For that reason, chemists there sought patentable analogues which might have advantages compared to the Rothamsted insecticides by having wider spectrum or greater cost-benefit. The first breakthrough was made when a trifluoromethyl group was used to replace one of the chlorines in cypermethrin, especially when the double bond was in its Z form. The second relied on a process chemists developed to practically manufacture the Z-cis acid by controlling the stereochemistry of the cyclopropane ring in addition to that of the double bond. [6] This led to the commercialisation of cyhalothrin and made available a relatively large supply of the acid. Exploratory studies continued in which it was combined with a large number of commercially available benzyl alcohols. In the main, these had little or no biological activity but when penta-fluorobenzyl alcohol was used the ester with X=F not only had substantial intrinsic activity on Diabrotica balteata but continued to be effective when soil was present, in contrast to other known pyrethroids. Further research allowed the analogue with X=CH3 (i.e. what became tefluthrin) to be identified after field trials as the optimum for development under the ICI code number PP993. [5] It was first marketed in 1987 using the trademark Force. [11] In 2000, the agrochemical business of ICI merged with that of Novartis to form Syngenta, which still manufactures and supplies tefluthrin. The US patent covering the parent compound expired in November 2002. [12] Tefluthrin was registered for sale in the European Union until December 5, 2008, when it was added to a group of pesticides whose authorization was withdrawn and it could no longer be sold. [13] However, on January 1, 2012, it was re-approved for use. [14] [15]

Mechanism of action

Pyrethroid insecticides, including tefluthrin, disrupt the functioning of the nervous system in an organism. They are fast-acting axonic excitotoxins, which affect the voltage-gated sodium channels. [16] The sodium channels are heteromultimeric complexes consisting of one large 𝛼-subunit and two smaller 𝛽-subunits. The binding site of tefluthrin is on the 𝛼-subunit, which also forms the pore of the channel. It alters the functioning of the channel by blocking the inactivation and slowing the deactivation. [17] This results in persistent and prolonged activation of sodium channels and inflow of sodium, which is lethal to the insect. There are many different forms of sodium channels: in mammals, nine different sodium channel 𝛼-subunits have been identified (named Nav1.1-Nav1.9). [18] The channel isoforms differ in affinity for tefluthrin; for example the Nav1.6 is at least 15-fold more sensitive than the Nav1.2 isoform. [19] [20]

Formulations

Tefluthrin is made available to end-users only in formulated products. Its main use is for the control of soil-dwelling insects in maize when formulated as granules. [21] It can also be incorporated in seed treatments.

Usage

All pesticides are required to seek registration from appropriate authorities in the country in which they will be used. [22] In the United States, the Environmental Protection Agency (EPA) is responsible for regulating pesticides under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) and the Food Quality Protection Act (FQPA). [23] A pesticide can only be used legally according to the directions on the label that is included at the time of the sale of the pesticide. The purpose of the label is "to provide clear directions for effective product performance while minimizing risks to human health and the environment". A label is a legally binding document that mandates how the pesticide can and must be used and failure to follow the label as written when using the pesticide is a federal offense. [24] The current (2020) label for tefluthrin in the USA covers its use on field corn, popcorn, seed corn and sweetcorn and specifies the amount to be applied. [25] Within the European Union, a 2-tiered approach is used for the approval and authorisation of pesticides. Firstly, before a formulated product can be developed for market, the active substance must be approved for the European Union. After this has been achieved, authorisation for the specific product must be sought from every Member State that the applicant wants to sell it to. Afterwards, there is a monitoring programme to make sure the pesticide residues in food are below the limits set by the European Food Safety Authority.

Adult stages of some Diabrotica pests controlled by tefluthrin Diabrotica undecimpunctata howardi and D. barberi and D. virgifera virgifera.jpg
Adult stages of some Diabrotica pests controlled by tefluthrin

The main use of tefluthrin is to control the larvae of corn rootworms ( Diabrotica spp) and it is also lethal to cutworm and wireworm larvae. Related insects share this susceptibility to the compound, including pests such as springtails, symphylids, millipedes, pygmy beetle, fire ants and white grubs. [1] The advantage to the farmer comes in the form of improved yield at harvest. Farmers can act in their best economic interest: the value of the additional yield can be estimated and the total cost of using the insecticide informs the decision to purchase. This cost-benefit analysis by the end user sets a maximum price which the supplier can demand. The estimated annual use of tefluthrin in US agriculture is mapped by the US Geological Survey. [26] This shows that use peaked in 2003 but by 2017, the latest date for which figures are available, has fallen to about 150,000 pounds (68,000 kg) annually, almost exclusively in the corn belt. The ability of tefluthrin to control soil pests, in contrast to other pyrethroids, is due to its relatively high volatility, which allows its vapour to move from the site of application to the surrounding soil. [5] Its vapour pressure at 20 °C is 8.4 mPa while that of permethrin, for example, is 0.007 mPa. [1]

Human safety

Tefluthrin is a restricted use pesticide. One consequence of this is that, in the US, it is a violation of Federal law to use the product in a manner inconsistent with its labelling and the labelling must be in possession of the user at the time of the application. It can be absorbed into the body by inhalation of dust or mist and by ingestion. It causes moderate eye irritation. Prolonged or frequently repeated skin contact may cause allergic reactions in some individuals. Skin exposure may result in a transient sensation described as a tingling, itching, burning, or prickly feeling. Onset may occur immediately to four hours after exposure and may last 2–30 hours, without apparent skin damage. [25] First aid measures are included with the label information. [25]

Metabolism

The mammalian LD50 is 21.8 mg/kg (rats, oral). [1] Phase I metabolism of tefluthrin proceeds via both oxidation and hydrolysis. [27] Initial targets for oxidation are its methyl groups. Those on the cyclopropane ring and on the tetrafluorobenzene ring are oxidized to alcohol groups which can be further oxidized into carboxylic acids. Hydrolysis of tefluthrin occurs at the ester bond which results in cyhalothrin acid and 4-methyl-2,3,5,6-tetrafluorobenzyl alcohol, which can be further oxidized into the corresponding carboxylic acid. In phase II metabolism, the phase I metabolites are glucuronidated on any available alcohol groups to facilitate membrane transport and eventually excretion.

Environmental effects

Tefluthrin is very highly toxic to freshwater and estuarine fish and invertebrates. [25] Its properties and effects on the environment have been summarized in several publications. [1] [2] [28] Ultimately it is the regulatory authorities in each country who must weigh up the benefits to end users and balance these against the compound's inherent hazards and consequent risks to consumers and the wider environment. These authorities stipulate the conditions under which tefluthrin may be used.

Resistance management

Species have the ability to evolve and develop resistance to pyrethroids (and, indeed, almost all pesticides). This potential can be mitigated by careful management. Reports of individual pest species becoming resistant to tefluthrin are monitored by manufacturers, regulatory bodies such as the EPA and the Insecticide Resistance Action Committee (IRAC). [29] In some cases, the risks of resistance developing can be reduced by using a mixture of two or more insecticides which each have activity on relevant pests but with unrelated mechanisms of action. IRAC assigns insecticides into classes so as to facilitate this.

Related Research Articles

<span class="mw-page-title-main">Insecticide</span> Pesticide used against insects

Insecticides are pesticides used to kill insects. They include ovicides and larvicides used against insect eggs and larvae, respectively. Acaricides, which kill mites and ticks, are not strictly insecticides, but are usually classified together with insecticides. The major use of Insecticides is agriculture, but they are also used in home and garden, industrial buildings, vector control and control of insect parasites of animals and humans. Insecticides are claimed to be a major factor behind the increase in the 20th-century's agricultural productivity. Nearly all insecticides have the potential to significantly alter ecosystems; many are toxic to humans and/or animals; some become concentrated as they spread along the food chain.

<span class="mw-page-title-main">Cypermethrin</span> Chemical compound

Cypermethrin (CP) is a synthetic pyrethroid used as an insecticide in large-scale commercial agricultural applications as well as in consumer products for domestic purposes. It behaves as a fast-acting neurotoxin in insects. It is easily degraded on soil and plants but can be effective for weeks when applied to indoor inert surfaces. It is a non-systemic and non-volatile insecticide that acts by contact and ingestion, used in agriculture and in pest control products. Exposure to sunlight, water and oxygen will accelerate its decomposition. Cypermethrin is highly toxic to fish, bees and aquatic insects, according to the National Pesticides Telecommunications Network (NPTN). It is found in many household ant and cockroach killers, including Raid, Ortho, Combat, ant chalk, and some products of Baygon in Southeast Asia.

Pyrethrum was a genus of several Old World plants now classified in either Chrysanthemum or Tanacetum which are cultivated as ornamentals for their showy flower heads. Pyrethrum continues to be used as a common name for plants formerly included in the genus Pyrethrum. Pyrethrum is also the name of a natural insecticide made from the dried flower heads of Chrysanthemum cinerariifolium and Chrysanthemum coccineum. The insecticidal compounds present in these species are pyrethrins.

<span class="mw-page-title-main">Pyrethrin</span> Class of organic chemical compounds with insecticidal properties

The pyrethrins are a class of organic compounds normally derived from Chrysanthemum cinerariifolium that have potent insecticidal activity by targeting the nervous systems of insects. Pyrethrin naturally occurs in chrysanthemum flowers and is often considered an organic insecticide when it is not combined with piperonyl butoxide or other synthetic adjuvants. Their insecticidal and insect-repellent properties have been known and used for thousands of years.

<span class="mw-page-title-main">Bifenthrin</span> Chemical compound

Bifenthrin is a pyrethroid insecticide. It is widely used against ant infestations.

<span class="mw-page-title-main">Pyrethroid</span> Class of insecticides

A pyrethroid is an organic compound similar to the natural pyrethrins, which are produced by the flowers of pyrethrums. Pyrethroids are used as commercial and household insecticides.

<span class="mw-page-title-main">Permethrin</span> Medication and insecticide

Permethrin is a medication and an insecticide. As a medication, it is used to treat scabies and lice. It is applied to the skin as a cream or lotion. As an insecticide, it can be sprayed onto outer clothing or mosquito nets to kill the insects that touch them.

<span class="mw-page-title-main">Acaricide</span> Agent that kills members of the arachnid subclass Acari

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<span class="mw-page-title-main">Deltamethrin</span> Chemical compound

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<span class="mw-page-title-main">Cyhalothrin</span> Synthetic pyrethroid used as insecticide

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<span class="mw-page-title-main">Cyfluthrin</span> Chemical compound

Cyfluthrin is a pyrethroid insecticide and common household pesticide. It is a complex organic compound and the commercial product is sold as a mixture of isomers. Like most pyrethroids, it is highly toxic to fish and invertebrates, but it is far less toxic to humans. It is generally supplied as a 10–25% liquid concentrate for commercial use and is diluted prior to spraying onto agricultural crops and outbuildings.

ATCvet code QP53Ectoparasiticides, including insecticides and repellents is a therapeutic subgroup of the Anatomical Therapeutic Chemical Classification System for veterinary medicinal products, a system of alphanumeric codes developed by the World Health Organization (WHO) for the classification of drugs and other medical products for veterinary use. Subgroup QP53 is part of the anatomical group QP Antiparasitic products, insecticides and repellents.

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<span class="mw-page-title-main">Thiamethoxam</span> Chemical compound

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<span class="mw-page-title-main">Fenpropathrin</span> Chemical compound

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<span class="mw-page-title-main">Fomesafen</span> PPOi herbicide

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References

  1. 1 2 3 4 5 6 Pesticide Properties Database. "Tefluthrin". University of Hertfordshire.
  2. 1 2 "Tefluthrin". US National Library of Medicine. Retrieved 2020-02-02.
  3. ↑ "Compendium of Pesticide Common Names: tefluthrin". BCPC.
  4. ↑ Metcalf, Robert L.; Horowitz, Abraham R. (2014). "Insect Control, 1. Fundamentals". Ullmann's Encyclopedia of Industrial Chemistry. Wiley-VCH. doi:10.1002/14356007.a14_263.
  5. 1 2 3 McDonald, E.; Punja, N.; Jutsum, A. R. (1986). "Rationale in the invention and optimization of tefluthrin, a pyrethroid for use in soil". British Crop Protection Conference--Pests and Diseases, Proceedings (1): 199–206.
  6. 1 2 GBwithdrawn 2085000,Crosby, John,"An improved process for the preparation of certain cyclopropane pyrethroid intermediates having a high cis-content",published 1982-04-21, assigned to ICI plc
  7. ↑ USpatent 4551546,Punja, N, assigned to ICI plc
  8. ↑ McDonald, Edward; Punja, Nazim (1986). "A note on the synthesis and biological activity of polyfluorobenzyl pyrethroid esters". Pesticide Science. 17 (4): 459–463. doi:10.1002/ps.2780170418.
  9. ↑ Milner, D.J. (1989). "Routes to the insecticides tefluthrin: Unusual steps on the road to the 4-methyl-2,3,5,6-tetrafluorobenzyl unit". Journal of Fluorine Chemistry. 45: 107. doi:10.1016/S0022-1139(00)84479-6.
  10. ↑ Elliott, Michael (1977). "Synthetic pyrethroids". ACS Symposium Series. Vol. 42. American Chemical Society,Washington. pp. 1–28. doi:10.1021/bk-1977-0042.ch001. ISBN   978-0-8412-0368-6.
  11. ↑ "Syngenta: Celebrating 75 years of scientific excellence at Jealott's Hill International Research Centre" (PDF). Syngenta. 2003. Archived from the original (PDF) on October 11, 2007.
  12. ↑ "US4551546, Halogentated esters".
  13. ↑ "EUR-Lex - 32008D0934 - EN". eur-lex.europa.eu. 2008-12-05.
  14. ↑ "EUR-Lex - 02008D0934-20120101 - EN". 2012-01-01.
  15. ↑ "EU Pesticides database - European Commission". ec.europa.eu.
  16. ↑ Tan, Jianguo; Soderlund, David M. (2008). "Human and Rat Nav1.3 Voltage-Gated Sodium Channels Differ in Inactivation Properties and Sensitivity to the Pyrethroid Insecticide Tefluthrin". Neurotoxicology. 30 (1): 81–89. doi:10.1016/j.neuro.2008.10.008. ISSN   0161-813X. PMC   2696113 . PMID   19026681.
  17. ↑ Trainer, Vera L.; Mcphee, Jancy C.; Boutelet-Bochan, Helene; Baker, Carl; Scheuer, Todd; Babin, Didier; Demoute, Jean-Pierre; Guedin, Denis; Catterall, William A. (1 April 1997). "High Affinity Binding of Pyrethroids to the α Subunit of Brain Sodium Channels". Molecular Pharmacology. 51 (4): 651–657. doi:10.1124/mol.51.4.651. ISSN   0026-895X. PMID   9106631. S2CID   89494224.
  18. ↑ Goldin, Alan L.; Barchi, Robert L.; Caldwell, John H.; Hofmann, Franz; Howe, James R.; Hunter, John C.; Kallen, Roland G.; Mandel, Gail; Meisler, Miriam H.; Netter, Yoheved Berwald; Noda, Masahara; Tamkun, Michael M.; Waxman, Steven G.; Wood, John N.; Catterall, William A. (1 November 2000). "Nomenclature of Voltage-Gated Sodium Channels". Neuron. 28 (2): 365–368. doi: 10.1016/S0896-6273(00)00116-1 . ISSN   0896-6273. PMID   11144347.
  19. ↑ Tan, Jianguo; Soderlund, David M. (15 September 2010). "Divergent actions of the pyrethroid insecticides S-bioallethrin, tefluthrin, and deltamethrin on rat Nav1.6 sodium channels". Toxicology and Applied Pharmacology. 247 (3): 229–237. doi:10.1016/j.taap.2010.07.001. ISSN   0041-008X. PMC   2929565 . PMID   20624410.
  20. ↑ Klaassen, Curtis D., ed. (2001). Casarett and Doull's toxicology: the basic science of poisons (6th. ed.). New York: McGraw-Hill, Medical Pub. Division. ISBN   978-0-07-134721-1.
  21. ↑ "Force 6.5g insecticide". Syngenta United States. Retrieved 2020-02-02.
  22. ↑ Willson HR (1996). "Pesticide Regulations". In Radcliffe EB, Hutchison WD, Cancelado RE (eds.). Radcliffe's IPM World Textbook. St. Paul: University of Minnesota. Archived from the original on July 13, 2017.
  23. ↑ "Pesticides and Public Health". Pesticides: Health and Safety. US EPA. 2015-08-20. Archived from the original on January 14, 2014. Retrieved 2020-02-04.
  24. ↑ EPA (27 February 2013). "The Pesticide Label" . Retrieved 2020-02-04.
  25. 1 2 3 4 "Force 6.5g". Syngenta United States. Retrieved 2020-02-02.
  26. ↑ US Geological Survey (2020-06-18). "Estimated Agricultural Use for tefluthrin, 2017" . Retrieved 2020-09-04.
  27. ↑ Marrs, Tim (2012). Mammalian Toxicology of Insecticides. Cambridge: The Royal Society of Chemistry. pp. 156–158. ISBN   978-1-84973-300-7.
  28. ↑ Tefluthrin. Pest Management Regulatory Agency. 2010. p. 116. ISBN   978-1-100-14618-8.
  29. ↑ "IRAC website".

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