Simetryn

Common name: simetryn; simetryne
IUPAC name: N2,N4-diethyl-6-methylthio-1,3,5-triazine-2,4-diamine; 2,4-bis(ethylamino)-6-methylthio-1,3,5-triazine
Chemical Abstracts name: N,N'-diethyl-6-(methylthio)-1,3,5-triazine-2,4-diamine
CAS RN: [1014-70-6]

PHYSICAL CHEMISTRY
Mol. wt.: 213.3; M.f.: C8H15N5S; Form: Whitish crystals. M.p.: 82-83 ºC; V.p.: 9.5x10-2 mPa (20 ¯C). KOW: logP = 2.6 (calc., unionised). Henry: 5.07x10-5 Pa m3 mol-1 (calc.) S.g./density: 1.02; Solubility: In water 400 mg/l (20 ¯C). In methanol 380, acetone 400, toluene 300, n-hexane 4, n-octanol 160 (all in g/l, 20 ¯C). pKa: 4.0, weak base.

APPLICATIONS
Biochemistry: Photosynthetic electron transport inhibitor at the photosystem II receptor site.
Mode of action: Selective herbicide.
Uses: Used in combination with thiobencarb to control broad-leaved weeds in rice.
Formulation types: GR.

MAMMALIAN TOXICOLOGY
Oral: Acute oral LD50 for rats 750-1195 mg/kg.
Skin and eye: Acute percutaneous LD50 for rats >3200 mg/kg. Not a skin or eye irritant (rabbits).
NOEL: (2 y) for rats 1.2 mg/kg daily (2.5 mg/kg b.w.), mice 56 mg/kg daily, dogs 10.5 mg/kg daily.
ADI: 0.025 mg/kg b.w. (provisional value).
Toxicity class: WHO (a.i.) III; EPA (formulation) III
EC hazard: Xn; R22| N; R50, R53

ECOTOXICOLOGY
Fish: LC50 (96 h) for trout 7, guppy 5.2 ppm.
Algae: Toxic.
Bees: Non-toxic.

ENVIRONMENTAL FATE
Animals: DT50 in rats c. 10 h. Excreted in urine and faeces; two oxidative metabolic pathways.
Plants: Selectivity and metabolism of simetryn reviewed.