Fomesafen

Source: Wikipedia, the free encyclopedia.
Fomesafen
Names
Preferred IUPAC name
5-[2-Chloro-4-(trifluoromethyl)phenoxy]-N-(methanesulfonyl)-2-nitrobenzamide
Identifiers
3D model (
JSmol
)
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard
 100.069.470 Edit this at Wikidata
EC Number
  • 276-439-9
KEGG
UNII
  • InChI=1S/C15H10ClF3N2O6S/c1-28(25,26)20-14(22)10-7-9(3-4-12(10)21(23)24)27-13-5-2-8(6-11(13)16)15(17,18)19/h2-7H,1H3,(H,20,22)
    Key: BGZZWXTVIYUUEY-UHFFFAOYSA-N
  • CS(=O)(=O)NC(=O)C1=C(C=CC(=C1)OC2=C(C=C(C=C2)C(F)(F)F)Cl)[N+](=O)[O-]
Properties[1]
C15H10ClF3N2O6S
Molar mass 438.76 g·mol−1
50 mg/L (20 °C)
log P -1.2 (20 °C)
Acidity (pKa) 2.83
Hazards
GHS labelling:
GHS07: Exclamation mark
Warning
H302
P264, P270, P301+P312, P330, P501
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Fomesafen is the

inhibiting the enzyme protoporphyrinogen oxidase (PPO)[3] which is necessary for chlorophyll synthesis. Soybeans naturally have a high tolerance to fomesafen,[3][4] via metabolic disposal by glutathione S-transferase.[3][4] As a result, soy is the most common crop treated with fomesafen, followed by other beans and a few other crop types.[5] It is not safe for maize/corn[6] or other Poaceae.[4]

History

The nitrophenyl ethers are a well-known class of herbicides, the oldest member of which was

brand name Mowdown in 1981. Meanwhile Rohm & Haas introduced acifluorfen (as its sodium salt with brand name Blazer) in 1980, having developed it under the code number RH-6201.[9] It had much improved properties including a wider spectrum of herbicidal effect and good safety to soybean crops. The first patent for the material was published in December 1975,[10] although an earlier Belgian patent published in September 1973 had described related chemistry.[11]

  • Nitrofen
    Nitrofen
  • Bifenox
    Bifenox
  • Acifluorfen
    Acifluorfen

Chemists at the

metabolise to acifluorfen and potentially infringe the competitor's patents. Patent filings on this invention, where the replacement for COOH was a CONHSO2CH3 group were made in January 1978.[12] Fomesafen was developed under the code number PP021 and first sales were in Argentina in 1983, with the brand name Flex.[1]

Synthesis

As described in the ICI patent,

acid chloride
and then with methanesulfonamide, in pyridine as solvent.

Ar-COOH + SOCl2 → ArCOCl
Ar-COCl + CH3SO2NH2 → ArCONHSO2CH3

Mechanism of action

The detailed mechanism of action for fomesafen and related nitrophenyl ether herbicides was unknown at the time they were invented. The effects visible on whole plants are chlorosis and desiccation: several hypotheses were advanced regarding the molecular-level interactions which might explain these symptoms.[13] The now-accepted explanation for the damage is that these compounds inhibit the enzyme protoporphyrinogen oxidase, which leads to an accumulation of protoporphyrin IX in the plant cells. This is a potent photosensitizer which activates oxygen, leading to lipid peroxidation. Both light and oxygen are required for this process to kill the plant.[14][15]

Usage

In the United States, the Environmental Protection Agency (EPA) is responsible for regulating pesticides under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), the Food Quality Protection Act (FQPA) and the Pesticide Registration Improvement Act (PRIA). 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 offence.[16][17]

Fomesafen is normally applied postemergence (when weeds are visible in the crop) but may also be used preemergence. It controls or suppresses broadleaf weeds, grasses and sedges in soybeans and is effective on a very wide range of weed species including

Sorghum halepense, Striga asiatica and Xanthium strumarium. The product is typically used at application rates of 0.3 lb a.i. per acre.[17]

US Geological Survey estimate of fomesafen use in the USA to 2018

The estimated annual use of fomesafen in US agriculture is mapped by the US Geological Service and shows that in 2018, the latest date for which figures are available, approximately 6,000,000 pounds (2,700,000 kg) were applied — mainly in soybean.[18] The compound is not registered for use in the European Union, although a closely related nitrophenyl ether, bifenox, is available there.[19]

Human safety

The

LD50 of fomesafen is 1250 mg/kg (rats, oral), which means that it is moderately toxic by oral ingestion.[1] The US Code of Federal Regulations records the maximum residue tolerances for fomesafen in various food products.[20]

Effects on the environment

The environmental fate and ecotoxicology of fomesafen are summarised in the Pesticide Properties database[1] The compound was used in a case study that developed methods for conducting nationwide endangered species assessments in the USA.[21]

Resistance

Resistance to fomesafen has developed including in Amaranthus retroflexus in Northeast China,[22] Amaranthus palmeri in Arkansas,[23] and Euphorbia heterophylla in Brazil.[24]

References

  1. ^ a b c d Pesticide Properties Database. "Fomesafen". University of Hertfordshire. Retrieved 2021-03-03.
  2. ^ "Compendium of Pesticide Common Names: fomesafen". BCPC.
  3. ^ a b c "fomesafen". Weed Ecology and Management Laboratory at Cornell University. Retrieved 2020-11-22.
  4. ^
    ISSN 0031-613X
    .
  5. ^ "Registration Review Label Mitigation for Fomesafen" (PDF). United States Environmental Protection Agency.
  6. ^ "Fomesafen Carryover Injury to Corn". Iowa State University. 2014-06-03. Retrieved 2020-11-22.
  7. ^ Pesticide Properties Database. "Nitrofen". University of Hertfordshire. Retrieved 2021-03-03.
  8. ^ US patent 3784635, Theissen R.J., "Herbicidal 4-trifluoromethyl-4'-nitrodiphenyl ethers", issued 1974-01-08, assigned to Mobil Oil Corporation 
  9. ^ Pesticide Properties Database. "Acifluorfen-sodium". University of Hertfordshire. Retrieved 2021-03-03.
  10. ^ US patent 3928416, Bayer H. O.; Swithenbank C. & Yih R. Y., "Herbicidal 4-trifluoromethyl-4'-nitrodiphenyl ethers", issued 1975-12-23, assigned to Rohm & Haas 
  11. ^ BE patent 796677, Bayer H. O.; Swithenbank C. & Yih R. Y., "Nouveaux ethers 4-trifluoromethyl-4'-nitro-diphenyliques herbicides et leur application a la lutte contre les mauvaises herbes", issued 1973-09-13, assigned to Rohm & Haas 
  12. ^ a b EP patent 0003416, Cartwright D. & Collins D. J., "Diphenyl ether compounds useful as herbicides; methods of using them, processes for preparing them, and herbicidal compositions containing them.", issued 1981-08-26, assigned to ICI Ltd. 
  13. PMID 16663025
    .
  14. ISBN 978-3-642-63674-5
    .
  15. ISBN 978-3-642-63674-5
    .
  16. US EPA
    . 27 February 2013. Retrieved 2021-02-27.
  17. ^ a b Syngenta US. "Flexstar". syngenta-us.com. Retrieved 2021-03-02.
  18. ^ US Geological Survey (2021-10-12). "Estimated Agricultural Use for Fomesafen, 2018". Retrieved 2022-01-17.
  19. ^ Pesticide Properties Database. "Bifenox". University of Hertfordshire. Retrieved 2021-03-03.
  20. ^ "Fomesafen; tolerances for residues". ecfr.federalregister.gov. 2018-02-07. Retrieved 2021-03-05.
  21. ISBN 978-0-8412-2703-3
    .
  22. S2CID 216246076
    .
  23. PMID 26817647
    .
  24. S2CID 219415301
    .

External links

  • Fomesafen in the Pesticide Properties DataBase (PPDB)
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