Specifications

1) Cas No.:886-50-0
2) Appearance: White powder.
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Terbutryn

CAS #: 886-50-0

 

Categories:  Herbicides

 

Description:

NOMENCLATURE
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

PHYSICAL CHEMISTRY
Composition: Tech. is 98%.

Mol. wt.: 241.4;

M.f.: C₁₀H₁₉N₅S;

Form: White powder.

M.p.: 104-105C.

B.p.: 274C/101 kPa.

V.p.: 0.225 mPa (25C) (OECD 104).

KOW: logP = 3.65 (25 ^oC, unionised).

Henry: 1.5x10^-3 Pa m³ mol^-1 (calc.)

S.g./density: 1.12 (20C).

Solubility: In water 22 mg/l (22C). In acetone 220, hexane 9, n-octanol 130, methanol 220, toluene 45 (all in g/l, 20C). Also readily soluble in dioxane, diethyl ether, xylene, chloroform,

carbon tetrachloride, dimethylformamide. Slightly soluble in petroleumether.Stability:

Stable under normal conditions. The methylthio group is hydrolysed in the presence of

strong acids or alkalis. At 70C, no significant hydrolysisCcurs 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.