Difenoxuron

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Difenoxuron
Names
IUPAC name
3-[4-(4-Methoxyphenoxy)phenyl]-1,1-dimethylurea
Other names
N′-[4-(4-methoxyphenoxy)phenyl]-N,N-dimethylurea
Lironion
Identifiers
3D model (JSmol)
ChemSpider
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EC Number
  • 238-068-0
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UNII
  • {{#property:P3117}}Lua error in Module:EditAtWikidata at line 29: attempt to index field 'wikibase' (a nil value).
  • InChI=1S/C16H18N2O3/c1-18(2)16(19)17-12-4-6-14(7-5-12)21-15-10-8-13(20-3)9-11-15/h4-11H,1-3H3,(H,17,19)
    Key: AMVYOVYGIJXTQB-UHFFFAOYSA-N
  • CN(C)C(=O)NC1=CC=C(C=C1)OC2=CC=C(C=C2)OC
Properties
C16H18N2O3
Molar mass 286.331 g·mol−1
Appearance Solid white powder[1][2]
Density 1300 kg/m3[2]
Melting point 139 °C (282 °F; 412 K)[2]
Solubility Soluble in acetone
Hazards
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 0: Exposure under fire conditions would offer no hazard beyond that of ordinary combustible material. E.g. sodium chlorideFlammability 0: Will not burn. E.g. waterInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
0
0
0
Lethal dose or concentration (LD, LC):
>7750 mg/kg (rat, oral)
2150 mg/kg (rat, dermal)[3]
Safety data sheet (SDS) http://cdn.chemservice.com/product/msdsnew/External/English/N-12977%20English%20SDS%20US.pdf
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Difenoxuron (commercially known as Lironion) is a phenylurea herbicide used to control annual broad-leaved weeds and grasses in allium crops (predominantly onions),[4][5] carrots, jojoba, and celery.[6][7][8]

Production

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Difenoxuron may be synthesized from 4-chloroaniline, 4-methoxyphenol, dimethylamine, and phosgene.[9] It is stereochemically achiral.[10]

Mechanism of action

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Difenoxuron is a member of the phenylurea class of herbicides. Phenylureas inhibit photosynthesis at photosystem II by binding to the serine 264 residue of the D1 protein, occupying the Qb (secondary plastoquinone) binding site and hence halting electron transfer from the primary acceptor Qa to the secondary acceptor Qb.[11] This prevents CO2 fixation and energy production.[12] Moreover, this blockade prevents chlorophyll from transferring energy to Qa, increasing production of triplet-state chlorophyll, which reacts with molecular oxygen to form singlet oxygen, a highly reactive species that oxidatively damages the pigments, lipids and proteins of the photosynthetic thylakoid membrane.[12]

Herbicidal activity

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Liming in Boddington soil has been shown by a 1976 study to increase the herbicidal toxicity of difenoxuron by two to three times compared to soil without the additional level of liming.[13]

Toxicology

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Difenoxuron's hazards include acute toxicity caused by oral ingestion, and acute toxicity of inhalation. There are very few studies about the genotoxicity of difenoxuron and these studies are inconcordant but there appears to be a dose dependent relationship between the concentration of difenoxuron and rate of observed chromosomal aberrations.[5]

References

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