Triclopyr

Triclopyr (3,5,6-trichloro-2-pyridinyloxyacetic acid) is an organic compound in the pyridine group that is used as a systemic foliar herbicide[2] and fungicide.[3]

Triclopyr[1]
Skeletal formula of triclopyr
Space-filling model of the triclopyr molecule
Names
Preferred IUPAC name
[(3,5,6-Trichloropyridin-2-yl)oxy]acetic acid
Other names
3,5,6-TPA; Trident (Agriphar)
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.054.161
UNII
  • InChI=1S/C7H4Cl3NO3/c8-3-1-4(9)7(11-6(3)10)14-2-5(12)13/h1H,2H2,(H,12,13) ☒N
    Key: REEQLXCGVXDJSQ-UHFFFAOYSA-N ☒N
  • InChI=1/C7H4Cl3NO3/c8-3-1-4(9)7(11-6(3)10)14-2-5(12)13/h1H,2H2,(H,12,13)
    Key: REEQLXCGVXDJSQ-UHFFFAOYAE
  • ClC1=C(OCC(O)=O)N=C(Cl)C(Cl)=C1
  • C1=C(C(=NC(=C1Cl)Cl)OCC(=O)O)Cl
Properties
C7H4Cl3NO3
Molar mass 256.46 g·mol−1
Appearance Fluffy solid
Melting point 148 to 150 °C (298 to 302 °F; 421 to 423 K)
440 mg/L
Solubility in acetone 989 g/kg
Acidity (pKa) 2.68
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
☒N verify (what is checkY☒N ?)
Infobox references

Uses

Triclopyr is used to control broadleaf weeds while leaving grasses and conifers unaffected[2] or to control rust diseases on crops.[3]

Triclopyr is effective on woody plants and is used for brush control in the right-of-way and defoliation of wooded areas. In the USA, it is sold under the trade names Garlon, Remedy, and many others, and in the UK as SBK Brushwood Killer.

It is also used for broadleaf weeds, particularly creeping charlie (Glechoma hederacea). It is sold under the trade names Turflon, Weed-B-Gon (purple label), and Brush-B-Gon ("Poison Ivy Killer") for these purposes. It is a major ingredient in Confront, which was withdrawn from most uses due to concerns about compost contamination from the other major ingredient, clopyralid.

Environmental effects

Triclopyr breaks down in soil with a half-life between 30 and 90 days. It degrades rapidly in water, and remains active in decaying vegetation for about 3 months.[4]

The compound is slightly toxic to ducks (LD50 = 1698 mg/kg) and quail (LD50 = 3000 mg/kg).[5] It has been found nontoxic to bees and very slightly toxic to fish (rainbow trout LC50 (96 hr) = 117 ppm).[4]

Garlon's fact sheet for their triclopyr ester product indicates that triclopyr is highly toxic to fish, aquatic plants, and aquatic invertebrates, and should never be used in waterways, wetlands, or other sensitive habitats.[6] This is only for the triclopyr ester product, not for the triclopyr amine product.

References
  1. Merck Index, 11th Edition, 9572.
  2. Appleby, Arnold P.; Müller, Franz; Carpy, Serge (2001). "Weed Control". Ullmann's Encyclopedia of Industrial Chemistry. doi:10.1002/14356007.a28_165. ISBN 3-527-30673-0.
  3. Shanmugasundaram, S.; Yeh, C.C.; Hartman, G.L.; Talekar, N.S. (1991). Vegetable Soybean Research Needs for Production and Quality Improvement (PDF). Taipei: Asian Vegetable Research and Development Center. pp. 86–87. ISBN 9789290580478. Retrieved 6 February 2016.
  4. Environmental Fate Of Triclopyr, Carissa Ganapathy, Environmental Monitoring & Pest Management Branch Department of Pesticide Regulation Sacramento, CA (dead link 23 October 2023)
  5. EXTOXNET (Extension Toxicology Network), Oregon State University
  6. "Garlon XRT Herbicide" (PDF).
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