Fluazifop

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Fluazifop

Fluazifop-P (R isomer)
Names
IUPAC name
(2R)-2-(4-([5-(trifluoromethyl)-2-pyridyl]oxy)phenoxy)propanoic acid
Preferred IUPAC name
(2R)-2-(4-([5-(trifluoromethyl)pyridin-2-yl]oxy)phenoxy)propanoic acid
Other names
PP005, SL118
Identifiers
  • Compounds
  • (RS): Fluazifop
  • (R): Fluazifop-P
  • (R) butyl ester: Fluazifop-P butyl ester
3D model (
JSmol
)
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard
 100.130.325 Edit this at Wikidata
EC Number
  • (RS): 614-949-9
  • (R) butyl ester: 616-669-2
UNII
  • (RS): InChI=1S/C15H12F3NO4/c1-9(14(20)21)22-11-3-5-12(6-4-11)23-13-7-2-10(8-19-13)15(16,17)18/h2-9H,1H3,(H,20,21)
    Key: YUVKUEAFAVKILW-UHFFFAOYSA-N
  • (R): InChI=1S/C15H12F3NO4/c1-9(14(20)21)22-11-3-5-12(6-4-11)23-13-7-2-10(8-19-13)15(16,17)18/h2-9H,1H3,(H,20,21)/t9-/m1/s1
    Key: YUVKUEAFAVKILW-SECBINFHSA-N
  • (R) butyl ester: Key: VAIZTNZGPYBOGF-CYBMUJFWSA-N
  • (R): C[C@H](C(=O)O)Oc1ccc(cc1)Oc2ccc(cn2)C(F)(F)F
Properties[1]
C15H12F3NO4
Molar mass 327.259 g·mol−1
40.5 mg/L (20 °C)
log P 3.18
Acidity (pKa) 3.12
Hazards[2]
GHS labelling:
GHS08: Health hazardGHS09: Environmental hazard
Warning
H361, H410
P201, P202, P273, P281, P308+P313, P391, P405, P501
Flash point 225 °C (437 °F; 498 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Fluazifop is the

chiral centre and this material is known as fluazifop-P when used in that form. More commonly, it is sold as its butyl ester
, fluazifop-P butyl with the brand name Fusilade.

History

Further information: Phenoxy herbicide

In the 1970s, a number of

2,4-D
, which had activity on broad-leaved weeds but were safe to grass crops such as the cereals. Thus the aim was to find materials which would selectively control grass weeds in broad-leaved crops such as cotton and soybean.

Haloxyfop
: X = N, R1 = CF3, R2 = Cl

In 1973,

haloxyfop as its methyl ester.[5]
All these compounds have an additional oxygen-linked
phenyl ring with its OCH(CH3)COOH group and as a class are called "fops", referring to their common fenoxy-phenoxy [sic] feature.[6] (In other words, fops are a subtype of ACCase herbicides, specifically the aryloxyphenoxypropionates.)[7][8][9]

Synthesis

The preparation of fluazifop butyl ester as a

ethers with 2-chloro-5-trifluoromethyl pyridine and the butyl ester of 2-bromopropionic acid: these nucleophilic substitution reactions can be performed in either order. The compound is now sold in its single-enantiomer form by Syngenta and other manufacturers.[12] It is produced from chiral starting materials such as alanine and lactic acid.[13]

Mechanism of action

Fluazifop and other similar herbicides act by inhibiting plant

isoform of the enzyme present only in these species, making them ineffective on broad-leaved weeds and other organisms including mammals.[16] When applied as an ester, metabolism in the target plant leads to the parent acid which is responsible for the herbicidal action.[5]

Usage

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

The estimated annual use of fluazifop in US agriculture is mapped by the US Geological Service and shows that in 2018, approximately 200,000 pounds (91,000 kg) were applied — almost exclusively in soyabean. The earlier much higher figure is partly because the compound was initially used as its racemate.[17] The herbicide is also registered for use in the European Union under EC Regulation 1107/2009.[1][18]

Human safety

The

LD50 of fluazifop-P butyl is 2451 mg/kg (rats, oral), which means that it has low toxicity by oral ingestion. It metabolises in plants and soil to the parent acid, fluazifop-P.[1] The World Health Organization (WHO) and Food and Agriculture Organization (FAO) joint meeting on pesticide residues has determined that the acceptable daily intake for fluazifop is 0-0.004 mg/kg bodyweight.[19]
The Codex Alimentarius database maintained by the FAO lists the maximum residue limits for fluazifop in various food products, some of which are set at its 0.01 mg/kg limit of detection while others are much higher, including soyabean at 15 mg/kg.[20]

Effects on the environment

The environmental fate and

USDA Forest Service.[21]

Resistance Management

There are many reports of individual weed species becoming resistant to fluazifop[22][23] and other ACCase inhibitors.[8][9] These are monitored by manufacturers, regulatory bodies such as the EPA and the Herbicides Resistance Action Committee (HRAC).[24] In some cases, the risks of resistance developing can be reduced by using a mixture of two or more herbicides which each have activity on relevant weeds but with unrelated mechanisms of action. HRAC assigns active ingredients into classes so as to facilitate this.

References

  1. ^ a b c d e Pesticide Properties Database. "Fluazifop-P". University of Hertfordshire. Retrieved 2021-02-25.
  2. ^ PubChem Database. "Fluazifop". Retrieved 2021-02-25.
  3. ^ "Compendium of Pesticide Common Names: fluazifop". British Crop Production Council (BCPC).
  4. ^ Pesticide Properties Database. "Fluazifop-P butyl". University of Hertfordshire. Retrieved 2021-02-25.
  5. ^ a b Evans, D. (1992). "Designing more efficient herbicides" (PDF). Proceeding of the First International Weed Control Congress , Melbourne. pp. 37–38. Retrieved 2021-02-27.
  6. ^
    S2CID 152283206
    .
  7. ^ "aryloxyphenoxypropionic herbicides". alanwood.net. Retrieved 2021-02-27.
  8. ^
    S2CID 84631177
    .
  9. ^
    S2CID 42537130
    .
  10. ^ WO patent 7900094, Cartwright D., "Herbicidal pyridine compounds", assigned to ICI Ltd. 
  11. ^ GB patent 1599126, Ishihara Sangyo Kaisha Ltd, "An α-[4-(5-fluoromethyl-2-pyridyloxy)phenoxy]alkanecarboxylic acid derivative and its use as a herbicide", assigned to ISK Ltd. 
  12. ^ Syngenta. "Fusilade DX". Retrieved 2021-02-27.
  13. doi:10.1039/C4GC00797B
    .
  14. PMID 2902848
    .
  15. S2CID 27124700
    .
  16. PMID 12859251
    .
  17. ^ US Geological Survey (2021-10-12). "Estimated Agricultural Use for Fluazifop, 2018". Retrieved 2021-12-27.
  18. ^ "Substance Infocard, fluazifop-P-butyl". echa.europa.eu. Retrieved 2021-02-27.
  19. ISBN 9789251320860
    .
  20. ^ FAO / WHO. "Fluazifop-P butyl".
  21. ^ Durkin, Patrick R. (2014-07-21). "Scoping/Screening Level Risk Assessment on Fluazifop-P-butyl" (PDF). fs.fed.us. p. 275. Retrieved 2021-02-27.
  22. doi:10.1006/pest.1997.2265
    .
  23. doi:10.1111/wre.12118
    .
  24. ^ "Herbicides Resistance Action Committee website".

Further reading

  • Rao, V.S. (2017-06-29). Principles of Weed Science. CRC Press. p. 555.
    ISBN 9781138401570
    .
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