Tribenuron methyl

Chemical Properties

Tribenuron-methyl (TBM) is a member of the sulfonylurea herbicide family. It is a relatively polar, weak, acidic compound that is soluble in water. It can be extracted with polar organic solvent, buffer solution, or a mixture of organic solvent and water.
Tribenuron-methyl is a selective herbicide that inhibits the biosynthesis of branched amino acids in sensitive plants by competitively binding to the enzyme system which catalyzes the formation of these amino acids, the acetolactate synthase (ALS). It is used in cereals for the control of broadleaved weeds.

Uses

Tribenuron-methyl is a sulfonyl urea herbicide derivative employed for protection of crops such as corn, citrus, potatoes, tomatoes, rice and vines via inhibiting the growth of many grasses and broad-leaf weed species.Tribenuron-methyl is applied as a foliar spray and directly to the soil as it is rapidly absorbed by the foliage and the roots, and is translocated throughout the plant to the growing points.
Tribeneuron-methyl acts by inhibiting the synthesis of amino acids, specifically valine and isoleucine, which prevents cell division and cell growth. Selectivity occurs due to the differences in the metabolism of sulfonylureas between crops and weeds.
Methomyl is a broad spectrum carbamate insecticide with both contact and oral toxicity to control chewing and sucking Lepidotera, Homoptera, Coleoptera and Hemiptera pests in vegetable, orchard, vine and field crops.

Definition

ChEBI: The methyl ester of tribenuron.

General Description

Colorless crystals. Non corrosive. Used as an herbicide.

Air & Water Reactions

Hydrolysis occurs rapidly at pH <7 or >12.

Reactivity Profile

A sulfonylurea derivative.

Agricultural Uses

Herbicide: Used to control annual grasses and broadleaf weeds on barley, blueberries, oats, wheat, flax and rape seed (canola). Registered for use in EU countries . Registered for use in the U.S. U.S. Maximum Allowable Residue Levels for the residues of the herbicide tribenuron methyl [40 CFR 180.451(a)]: in or on the following raw agricultural commodities: barley, grain 0.05 ppm; barley, straw 0.10ppm; canola, seed 0.02 ppm; cotton, gin byproducts 0.02 ppm; cotton, undelinted seed 0.02 ppm; flax, seed 0.02 ppm; oat, grain 0.05 ppm; oat, straw 0.10ppm; wheat, grain 0.05ppm; and wheat, straw 0.10 ppm. Tolerances with regional registration, as defined in 180.1(n), are established. [40 CFR 180.451(c)]: in or on the following raw agricultural commodities: grass, forage, fodder and hay, group (except Bermudagrass); forage 0.10ppm; and grass, forage, fodder and hay, group (except Bermudagrass); hay 0.10 ppm.

Trade name

ALLY®; CANVAS®; DPX-L-5300®; EXPRESS®; EXPRESS®-75 DF; HARMONY EXTRA®; INL-5300®; L 5300®; MATRIX®

Metabolic pathway

The chemical structure of tribenuron methyl possesses a mono-N-methyl group in the sulfonylurea linkage which is a unique sulfonylurea herbicide and undergoes complex degradation reactions in the environment. Tribenuron methyl degrades into many degradation products, as indicated in the pathways by photolytic and hydrolytic chemical reactions and by biological degradations by mammal, plant, and soil. It is interesting to note that photolysis in different solvents yields diverse products depending on the individual solvents.

Degradation

Methomyl (1) was hydrolysed under alkaline conditions at 25 °C (DT₅₀ ca. 14 days) and was stable under neutral to acidic conditions [DT₅₀ > 30 days at pH 5 and 7 (Friedman, 1983)l. Cleavage of the carbamate ester bond is the primary degradation pathway, yielding S-methyl N-hydroxy-thioacetimidate (2).
Irradiation of methomyl in dilute aqueous solution at 254 nrn yielded acetonitrile (3), dimethyl disulfide, acetone, N-ethylidenethylamine and carbon dioxide (Freeman and Ndip, 1984). Methomyl does not absorb sunlight but underwent degradation to acetonitrile by indirect photolytic reactions in/on soil surfaces (Swanson, 1986).