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 (DT
50
ca. 14 days) and was stable under neutral to acidic conditions [DT
50 > 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).
