Metribuzin

Metribuzin
Names
	Preferred IUPAC name 3-Amino-5-tert-butyl-2-(methylsulfanyl)-1,2,4-triazin-5(4H)-one
	Other names 4-Amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin-5(4H)-one
Identifiers
CAS Number	21087-64-9 ;
3D model (JSmol)	Interactive image;
ChEBI	CHEBI:34846 ;
ChemSpider	28287;
ECHA InfoCard	100.040.175
PubChem CID	30479;
UNII	QO836138OV ;
CompTox Dashboard (EPA)	DTXSID6024204 ;
	InChI InChI=1S/C8H14N4OS/c1-8(2,3)5-6(13)12(9)7(14-4)11-10-5/h9H2,1-4H3 Key: FOXFZRUHNHCZPX-UHFFFAOYSA-N; InChI=1/C8H14N4OS/c1-8(2,3)5-6(13)12(9)7(14-4)11-10-5/h9H2,1-4H3 Key: FOXFZRUHNHCZPX-UHFFFAOYAI;
	SMILES CC(C)(C)C1=NN=C(N(C1=O)N)SC;
Properties
Chemical formula	C8H14N4OS
Molar mass	214.29 g·mol−1
Appearance	Colorless, crystalline solid
Density	1.31 g/cm3
Melting point	125 °C (257 °F; 398 K)
Solubility in water	0.1% (20 °C)
Vapor pressure	0.0000004 mmHg (20 °C)
Hazards
	NIOSH (US health exposure limits):
PEL (Permissible)	none
REL (Recommended)	5 mg/m3
IDLH (Immediate danger)	N.D.
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Metribuzin (4-amino-6-tert-butyl-3-(methylthio)-1,2,4-triazin-5(4H)-one) is a herbicide used both pre- and post-emergently in crops including soy bean, potatoes, tomatoes, barley, chickpeas, faba beans, lupins, lentils, vetch, blade wheat and sugar cane.^[2]

It is registered for use in Australia^[3] and India.^[4]

Mechanism

It destroys cells by inhibiting photosynthesis by disrupting photosystem II,^[5] which makes metribuzin's HRAC classification Group C1, Group C (global, Aus), Group 5 (numeric).^[6]^[2]

Herbicidal uptake in the plant is mostly by the roots, with some through the leaves. Metribuzin translocates upward, destroying cells. Symptoms on affected weeds occur in 7 to 30 days: chlorosis, followed by desiccation.^[2]

Application

Metribuzin can be applied via a boom spray at 80 to 100 litres per hectare, and will be rain-fast after 6 hours. Moisture or rainfall within a fortnight improves its efficacy if used as a post-emergent; pre-emergent use requires soil incorporation (such as by a plough) within 12 hours. Recommended application rates go from 75 g/Ha to 380 g/Ha (0.067-0.34 lb/acre). It has been sold formulated as wettable granules, and can be compatibly mixed with glyphosate, trifluralin, diflufenican, chlorsulfuron, metsulfuron and pendimethalin. Anecdotally, a mixture with simazine is effective against wild radish.^[2]

It is effective against the weeds of capeweed, common cotula, doublegee, fumitory, Indian hedge mustard, toad rush, wild radish, wild turnip and wireweed, and can provide suppression only of brome grass, annual ryegrass and barley grass.^[2]

Environmental behvaiour

It is widely used in agriculture and has been found to contaminate groundwater.^[7]

Synthesis

Metribuzin is produced by reacting one mole of 4-amino-6-tert-butyl-3-mercapto-(1,2,4)triazin-5(4H)one and half a mole of dimethyl sulfonate which react at 57°C in presence of sulfuric acid media about 7 hours and transfer methyl (CH₃) from triazine to metribuzin and product formed 1 mole of metribuzin and half mole of sulfuric acid and later neutralized with soda ash and then purified.

References

^ ^a ^b ^c ^d ^e ^f NIOSH Pocket Guide to Chemical Hazards. "#0430". National Institute for Occupational Safety and Health (NIOSH).
^ ^a ^b ^c ^d ^e "4Farmers Metribuzin 750 WG Infosheet" (PDF). 4farmers.com.au. 4Farmers Australia Pty. Retrieved 21 February 2026.
^ "4Farmers Metribuzin 750 WG". 4farmers.com.au. 4Farmers Australia Pty. Retrieved 21 February 2026.
^ Paranjape, Kalyani; Gowariker, Vasant; Krishnamurthy, V.N.; Gowariker, Sudha (2015). The Pesticide Encyclopedia. CABI. ISBN 978-1-78064-014-3.
^ Terence Robert Roberts; David Herd Hutson (17 July 1998). Metabolic Pathways of Agrochemicals: Herbicides and plant growth regulators. Royal Society of Chemistry. pp. 662–. ISBN 978-0-85404-494-8. Retrieved 25 May 2012.
^ "Classification of Herbicides According to Site of Action". Retrieved 19 July 2025.
^ Undabeytia, T. S.; Recio, E.; Maqueda, C.; Morillo, E.; Gómez-Pantoja, E.; Sánchez-Verdejo, T. (2011). "Reduced metribuzin pollution with phosphatidylcholine-clay formulations". Pest Management Science. 67 (3): 271–278. doi:10.1002/ps.2060. PMID 21308953.

External links

Metribuzin in the Pesticide Properties DataBase (PPDB)

[PGCH-1] ^ ^a ^b ^c ^d ^e ^f NIOSH Pocket Guide to Chemical Hazards. "#0430". National Institute for Occupational Safety and Health (NIOSH).

[4f_infosheet-2] "4Farmers Metribuzin 750 WG Infosheet" (PDF). 4farmers.com.au. 4Farmers Australia Pty. Retrieved 21 February 2026.

[3] "4Farmers Metribuzin 750 WG". 4farmers.com.au. 4Farmers Australia Pty. Retrieved 21 February 2026.

[4] Paranjape, Kalyani; Gowariker, Vasant; Krishnamurthy, V.N.; Gowariker, Sudha (2015). The Pesticide Encyclopedia. CABI. ISBN 978-1-78064-014-3.

[RobertsHutson1998-5] Terence Robert Roberts; David Herd Hutson (17 July 1998). Metabolic Pathways of Agrochemicals: Herbicides and plant growth regulators. Royal Society of Chemistry. pp. 662–. ISBN 978-0-85404-494-8. Retrieved 25 May 2012.

[6] "Classification of Herbicides According to Site of Action". Retrieved 19 July 2025.

[7] Undabeytia, T. S.; Recio, E.; Maqueda, C.; Morillo, E.; Gómez-Pantoja, E.; Sánchez-Verdejo, T. (2011). "Reduced metribuzin pollution with phosphatidylcholine-clay formulations". Pest Management Science. 67 (3): 271–278. doi:10.1002/ps.2060. PMID 21308953.

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