Specification :

Prometryn

Common name: prometryn; prometryne
IUPAC name: N2, N4-di-isopropyl-6-methylthio-1, 3, 5-triazine-2, 4-diamine
Chemical Abstracts name: N, N' -bis( 1-methylethyl) -6-( methylthio) -1, 3, 5-triazine-2, 4-diamine
CAS RN: [ 7287-19-6]

PHYSICAL CHEMISTRY
Composition: Tech. is 96% pure. Mol. wt.: 241.4; M.f.: C10H19N5S; Form: White powder. M.p.: 118-120 º C; B.p.: > 300 ° C/ 100 kPa. V.p.: 0.165 mPa ( 25 º C) ( OECD 104) . KOW: logP = 3.1 ( 25 º C, unionised) . Henry: 1.2x10-3 Pa m3 mol-1 ( calc.) S.g./ density: 1.15 ( 20 º C) . Solubility: In water 33 mg/ l ( 25 º C) . In acetone 300, ethanol 140, hexane 6.3, toluene 200, n-octanol 110 ( all in g/ l, 25 º C) . Stability: Stable to hydrolysis at 20 º C in neutral, slightly acidic or slightly alkaline media. Hydrolysed by warm acids and alkalis. Decomposed by u.v. irradiation. pKa: 4.1, weak base.

APPLICATIONS
Biochemistry: Photosynthetic electron transport inhibitor at the photosystem II receptor site. Also inhibits oxidative phosphorylation.
Mode of action: Selective systemic herbicide, absorbed by the leaves and roots, with translocation acropetally through the xylem from the roots and foliage, and accumulation in the apical meristems.
Uses: Used pre-emergence, at 0.8-2.5 kg/ ha, in cotton, sunflowers, peanuts, potatoes, carrots, peas and beans; post-emergence, at 0.8-1.5 kg/ ha, in cotton, potatoes, carrots, celery and leeks.
Phytotoxicity: Used as a directed spray on cotton while young, to avoid foliar injury.
Formulation types: FW; SC; WP.

MAMMALIAN TOXICOLOGY
Oral: Acute oral LD50 for rats > 2000 mg/ kg.
Skin and eye: Acute percutaneous LD50 for rats > 3100, rabbits > 2020 mg/ kg. Not irritant to skin and slightly irritant to eyes of rabbits. Not a skin sensitiser ( guinea pigs) .
Inhalation: LC50 ( 4 h) for rats > 5170 mg/ m3.
NOEL: ( 2 y) for rats 750, dogs 150 ppm; ( 21 mo) for mice 10 ppm.
ADI: 0.01 mg/ kg.
Toxicity class: WHO ( a.i.) III ( Table 5) ; EPA ( formulation) III ( 80 WP) , II ( 4 L)

ECOTOXICOLOGY
Birds: Dietary LC50 ( 8 d) for bobwhite quail > 5000, mallard ducks > 500 ppm.
Fish: LC50 ( 96 h) for rainbow trout 5.5, bluegill sunfish 7.9 mg/ l.
Daphnia: LC50 ( 48 h) 12.66 mg/ l.
Algae: EC50 ( 5 d) for Selenastrum capricornutum 0.023 mg/ l.
Other aquatic spp.: EC50 for mysid shrimp ( Mysidopsis bahia) 1.7 mg/ l.
Bees: Not toxic to bees. LD50 ( oral) > 99 ug/ bee; ( contact) > 130 ug/ bee.
Worms: LC50 ( 14 d) for earthworms 153 mg/ kg soil.

ENVIRONMENTAL FATE
Plants: Metabolised by tolerant plants, and, to a lesser extent, by sensitive plants, by oxidation of the methylthio group to hydroxy metabolites, and by dealkylation of the side-chains. Degradation in plants is generally slow.
Soil/ Environment: In soil, microbial degradation takes place, with oxidation of the methylthio group to hydroxy metabolites, and dealkylation of the side-chains. Median DT50 in soil 50 d ( 14-158 d) . Koc 400, indicating low mobility in soil. Degradation in aquatic systems is caused by microbial processes; further dissipation results from adsorption to the suspended and bottom sediments.