Tefluthrin
 tefluthrin (racemic)
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| Names | |
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| Preferred IUPAC name
(2,3,5,6-Tetrafluoro-4-methylphenyl)methyl rac-(1R,3R)-2,2-dimethyl-3-[(1Z)-2-chloro-3,3,3-trifluoroprop-1-en-1-yl]cyclopropane-1-carboxylate | |
| Other names
Tefluthrine
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| Identifiers | |
3D model (JSmol)
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| ChEBI | |
| ChEMBL | |
| ChemSpider | |
| ECHA InfoCard | 100.124.968 
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| EC Number |
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| KEGG | |
PubChem CID
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| UNII | |
CompTox Dashboard (EPA)
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| Properties[1] | |
| C17H14ClF7O2 | |
| Molar mass | 418.74 g·mol−1 |
| Appearance | colorless 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: | |
 
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Signal word
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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). | |
| Infobox references | |
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]
Synthesis[]
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 process chemists developed a practical manufacturing process for 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