Tefluthrin

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Tefluthrin
Tefluthrin.svg
Names
IUPAC name
(1S,3S)-rel-2,3,5,6-Tetrafluoro-4-methylbenzyl 3-((Z)-2-chloro-3,3,3-trifluoroprop-1-en-1-yl)-2,2-dimethylcyclopropanecarboxylate
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.124.968
Properties
C17H14ClF7O2
Molar mass 418.74 g·mol−1
Appearance colorless solid[1]
Density 1.48 g/mL[1]
Melting point 44.6 °C[1]
Boiling point 156 °C[1]
0.02 mg/L in water

>500 g/L in acetone, hexane, toluene, dichloromethane and ethyl acetate[1]

Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Tefluthrin is an organic compound. It is classified as a pyrethroid, meaning that in terms of chemical structure, it resembles the naturally occurring insecticide pyrethrin. It was designed to be effective against soil pests.[2] With an LD50 for rats of 29 mg/kg, tefluthrin is one of the most toxic pyrethroids.[3] Tefluthrin functions through binding to the voltage-gated sodium channels of organisms and thereby increasing the inflow of sodium into the cells.[4]

History[edit]

Tefluthrin was introduced for legalisation in the European Union in 1986 in Belgium. It took, however, until December 5, 2008 to add tefluthrin to a group of substances which are authorized as plant protection products.[5] On January 1, 2012 tefluthrin was re-approved for use in the European Union.[6]

Synthesis[edit]

Tefluthrin is a polyfluoroaryl carbinol, consisting of an aryl group with multiple fluoride atoms and a carbon chain attached. One way of synthesising polyfluoroaryl carbinols is by direct C-H metalation of fluorated arenes and addition to aldehydes. However, the multiple C-H metalations proved to be difficult without the right directing group. Magnesated polyfluoroaryl carbinols were used by scientists from the Key laboratory of Macromolecular Science of Shaanxi Province in China to mimic a Grignard reagent used to facilitate the mg prompted C-H metalation.

This method could be successfully executed with the Grignard reagent isopropylmagnesium bromide, isopropylmagnesium chloride, or ethylmagnesium bromide.The tefluthrin intermediate, 4-methyl-2,3,5,6-tetrafluorobenzyl alcohol, could be reacted with cis-Z 3-(2-chloro-l,l,l-trifluoro-2-propenyl)-2,2-dimethylcyclopropane carbonyl chloride to give tefluthrin.

Tefluthrin synthesis 2.png

Metabolism[edit]

Phase I metabolism of tefluthrin proceeds via both oxidation and hydrolysis.[7] Initial targets for oxidation are protruding methyl groups. These methyl groups can specifically be found on the cyclopropane ring and on the tetrafluorobenzene ring and are oxidized to alcohol groups. These alcohol groups can be further oxidized into carboxylic acid groups. Hydrolysis of tefluthrin happens at the ester bond which results in a cyhalothric acid and a tetrafluorobenzene alcohol, which can be further oxidized into a carboxylic acid. In phase II metabolism, the phase I metabolites are glucuronidated on any available alcohol groups to facilitate membrane transport and eventually excretion.

Mechanisms of action[edit]

Pyrethroid insecticides, and therefore also tefluthrin, influence the voltage-gated sodium channels of organisms.[8] 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. Tefluthrin alters the functioning of the voltage-gated sodium channels by blocking the inactivation and slowing the deactivation of the channels.[9] This results in persistent and prolonged activation of sodium channels and inflow of sodium. However, there are many different forms of sodium channels. In mammals 9 different sodium channel 𝛼-subunits have been identified (named Nav1.1-Nav1.9).[10] 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.[11] Also the action of tefluthrin is stereoselective. The cis isomer is up to 10-fold more toxic than the trans isomer, and also the binding differs between both isomers.[12]

Efficacy[edit]

Tefluthrin provided consistently good results when applied properly against certain Cryptophagidae which is a family of beetles. It was tested on the Atomaria linearis that is a species of silken fungus beetle native to Europe.[13] Organisms that are related to these animals seem to share this susceptibility to the compound. This includes a lot of soil pests (springtails; symphylids; millipedes; pygmy beetle; fire ants; rootworms; wireworms; white grubs).[14] The effective dose is 60 ml with a 100.000 seeds. It is not allowed to higher this concentration because of resistance management. It is preferred over other Pyrethrins because of its effects on lots of soil pests, high selectivity and stimulation of growth according to Syngenta, the company which produces the insecticide.[15]

Side effects[edit]

The use of tefluthrin on soil pests can have several side effects. At first it was investigated if tefluthrin will spread due to rain. Heavy rainfall was stimulated in a model to see whether the tefluthrin will be adsorbed or not. In the used model 85% of the total used tefluthrin was recovered out of the simulated rain water. To conclude anything on the consequences of the real environment, more research is needed.[16] Secondly adsorption of the tefluthrin by plants is possible. This was investigated by measuring the yield of the corn fields were the tefluthrin was used. When normal corn was used there was a slight loss of yield. Which implies the tefluthrin will enter the plant and affect it. When genetically modified corn was used the yield was not affected by tefluthrin.[17]

Symptoms of poisoning[edit]

Symptoms of poisoning with tefluthrin may include:

  • Irritation of skin and eyes
  • Irritability to sound or touch, abnormal facial sensation, sensation of prickling, tingling or creeping on skin, numbness
  • Headache, dizziness, nausea, vomiting, diarrhea, excessive salivation, fatigue
  • In severe cases: fluid in the lungs and muscle twitching may develop. Seizures may occur but are more common with more toxic cyano-pyrethroids

First Aid Measures[edit]

Incident Course of action
General advice Contact a doctor. Show this safety fact sheet to a doctor
Inhalation If breathed in, move person into fresh air. If not breathing, give artificial respiration. Contact a doctor
Contact with skin Wash off with soap and plenty of water. Take victim immediately to hospital. Contact a doctor
Contact with eyes Flush eyes with water as a precaution
If swallowed Never give anything by mouth to an unconscious person. Rinse mouth with water. Consult a doctor

References[edit]

  1. ^ a b c d e Hertfordshire, University of. "tefluthrin". sitem.herts.ac.uk.
  2. ^ 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.
  3. ^ D. M. Soderlund, et al., "Mechanisms of pyrethroid neurotoxicity: implications for cumulative risk assessment", Toxicology 2002, volume 171, pp. 3-59. doi:10.1016/s0300-483x(01)00569-8
  4. ^ Tan, J.; Soderlund, D. 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.
  5. ^ "EUR-Lex - 32008D0934 - EN - EUR-Lex". eur-lex.europa.eu.
  6. ^ "EU Pesticides database - European Commission". ec.europa.eu.
  7. ^ Marrs, Tim (2012). Mammalian Toxicology of Insecticides. Cambridge: The Royal Society of Chemistry. pp. 156–158. ISBN 978-1849733007.
  8. ^ 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.
  9. ^ 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.
  10. ^ 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.
  11. ^ 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.
  12. ^ Klaassen, editor, Curtis D. (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.CS1 maint: Extra text: authors list (link)
  13. ^ (PDF) http://nl-static-agro4all-com.s3.eu-central-1.amazonaws.com/product/13135/W2/3433f6e5-aa45-4b24-51db-4bc49e0f0278.pdf?token=1519764102. Missing or empty |title= (help)
  14. ^ Hertfordshire, University of. "tefluthrin". sitem.herts.ac.uk.
  15. ^ "Force 20CS | Syngenta Nederland". Syngenta Nederland (in Dutch). 22 August 2016.
  16. ^ Zhou, Jun L.; Rowland, Steve J.; Fauzi, R.; Mantoura, C.; Lane, Mike C.G. (1 January 1997). "Desorption of tefluthrin insecticide from soil in simulated rainfall runoff systems—Kinetic studies and modelling". Water Research. 31 (1): 75–84. doi:10.1016/S0043-1354(96)00237-0. ISSN 0043-1354.
  17. ^ Whiting, Sara A.; Strain, Katherine E.; Campbell, Laura A.; Young, Bryan G.; Lydy, Michael J. (1 November 2014). "A multi-year field study to evaluate the environmental fate and agronomic effects of insecticide mixtures". Science of the Total Environment. 497-498: 534–542. doi:10.1016/j.scitotenv.2014.07.115. ISSN 0048-9697. PMID 25163650.

External links[edit]

  • PPDB pesticides properties database of tefluthrin
  • MSDS of tefluthrin on sigma-aldrich
  • HSDB on toxnet