Specification :

Terbutryn

Common name: terbutryn; terbutryne
IUPAC name: N2-tert-butyl-N4-ethyl-6-methylthio-1, 3, 5-triazine-2, 4-diamine
Chemical Abstracts name: N-( 1, 1-dimethylethyl) -N' -ethyl-6-( methylthio) -1, 3, 5-triazine-2, 4-diamine
CAS RN: [ 886-50-0]

PHYSICAL CHEMISTRY
Composition: Tech. is 98% . Mol. wt.: 241.4; M.f.: C10H19N5S; Form: White powder. M.p.: 104-105 º C. B.p.: 274 ° C/ 101 kPa. V.p.: 0.225 mPa ( 25 º C) ( OECD 104) . KOW: logP = 3.65 ( 25 º C, unionised) . Henry: 1.5x10-3 Pa m3 mol-1 ( calc.) S.g./ density: 1.12 ( 20 º C) . Solubility: In water 22 mg/ l ( 22 º C) . In acetone 220, hexane 9, n-octanol 130, methanol 220, toluene 45 ( all in g/ l, 20 º C) . Also readily soluble in dioxane, diethyl ether, xylene, chloroform, carbon tetrachloride, dimethylformamide. Slightly soluble in petroleum ether. Stability: Stable under normal conditions. The methylthio group is hydrolysed in the presence of strong acids or alkalis. At 70 º C, no significant hydrolysis occurs at pH 5, 7, or 9. pKa: 4.3, weak base.

APPLICATIONS
Biochemistry: Photosynthetic electron transport inhibitor at the photosystem II receptor site.
Mode of action: Selective herbicide, absorbed by the roots and foliage, with translocation acropetally through the xylem, and accumulation in the apical meristems.
Uses: Used pre-emergence in winter cereals, at 1-2 kg a.i./ ha, to control blackgrass and annual meadow grass. Among the autumn-germinating broad-leaved weeds controlled are chickweed, mayweed, poppies and speedwell, but cleavers are rather resistant. Other pre-emergence uses are on sugar cane and sunflowers; and, in mixture with terbuthylazine, on beans, peas and potatoes. In mixture with metolachlor, used in cotton and peanuts. Also used post-emergence ( 0.2-0.4 kg/ ha) in cereals, ( 1-3 kg/ ha) in sugar cane, and as a directed spray in maize. As ' Clarosan' , it is used to control algae and submerged vascular plants in waterways, reservoirs and fish ponds.
Phytotoxicity: Not safe for post-emergence use in cereals which are under stress.
Formulation types: FW; GR; MG; SC; WP.

MAMMALIAN TOXICOLOGY
Oral: Acute oral LD50 for rats 2500, mice 500 mg/ kg.
Skin and eye: Acute percutaneous LD50 for rats > 2000, rabbits > 20 000 mg/ kg. Not a skin or eye irritant ( rabbits) . Not a skin sensitiser ( guinea pigs) .
Inhalation: LC50 ( 4 h) for rats > 2200 mg/ m3 air.
NOEL: ( 2 y) for rats 300 ppm, for mice 3000 ppm; ( 1 y) for dogs 100 mg/ kg diet daily.
ADI: 0.027 mg/ kg b.w.
Other: Non-mutagenic.
Toxicity class: WHO ( a.i.) III ( Table 5) ; EPA ( formulation) III

ECOTOXICOLOGY
Birds: Dietary LC50 ( 5 d) for bobwhite quail 5000, mallard ducks > 4640 mg/ kg b.w.
Fish: LC50 ( 96 h) for rainbow trout 1.1, bluegill sunfish 1.3, carp 1.4.
Daphnia: LC50 ( 48 h) 2.66 mg/ l.
Algae: EC50 ( 7 d) for Selenastrum capricornutum 0.013 mg/ l.
Other aquatic spp.: EC50 ( 48 h) for Quahog clam 5.6 mg/ l.
Bees: Not toxic to bees. LD50 ( oral) > 225 ug/ bee; ( contact) > 100 ug/ bee.
Worms: LC50 for Eisenia foetida 170 mg/ kg.

ENVIRONMENTAL FATE
Animals: In mammals, following oral administration, 73-85% is eliminated as the dealkylated hydroxy metabolite in the faeces within 24 hours.
Plants: In plants, terbutryn is degraded in a manner similar to other methylthio-s-triazines, viz. by oxidation of the methylthio group to hydroxy metabolites, and by dealkylation of the side-chains. Conjugates are also formed.
Soil/ Environment: Soil micro-organisms play an important role in the degradation of terbutryn. Residual activity in soil is 3-10 weeks, depending upon rate of application, soil type, and weather. DT50 in soil 14-50 d. Koc 2000, indicating a low leaching potential. Degradation in aquatic systems is caused by microbial processes; photolysis also contributes. Considerable amounts of terbutryn are removed from the water by adsorption to the sediment.