Herbicide
HRAC  F2 WSSA  28; triketone



NOMENCLATURE
Common name sulcotrione (BSI, pa E-ISO)
IUPAC name 2-(2-chloro-4-mesylbenzoyl)cyclohexane-1,3-dione 
Chemical Abstracts name 2-[2-chloro-4-(methylsulfonyl)benzoyl]-1,3-cyclohexanedione 
CAS RN [99105-77-8]  Development codes ICIA0051 (ICI); SC0051 

PHYSICAL CHEMISTRY
Composition Tech. material is 90% pure.  Mol. wt. 328.8  M.f. C₁₄H₁₃ClO₅S  Form White solid; (tech. is a light tan solid).  M.p. 139 ºC; (tech., 131-139 ºC)  V.p. 5 ×10^-3 mPa (25 ºC)  K_OW logP <0 (unspecified pH)  Henry 9.96 × 10^-6 Pa m³ mol^-1 (calc.)  Solubility In water 165 mg/l (25 ºC). Soluble in acetone and chlorobenzene.  Stability Stable in water, with or without exposure to sunlight. Thermostable up to 80 ºC.  pKa 3.13 (23 °C)

APPLICATIONS
Biochemistry p-Hydroxyphenyl pyruvate dioxygenase inhibitor.  Mode of action Herbicide, absorbed predominantly by the leaves, but also by the roots.  Uses Control of broad-leaved weeds and grasses post-emergence in maize and sugar cane, at 200-300 g/ha.  Formulation types SC.

MAMMALIAN TOXICOLOGY
Oral Acute oral LD₅₀ for rats >5000 mg/kg.  Skin and eye Acute percutaneous LD₅₀ for rabbits >4000 mg/kg. Low rate of absorption through the skin; non-irritating to skin; mild eye irritant (rabbits). Strong skin sensitiser (guinea pigs).  Inhalation LC₅₀ (4 h) >1.6 mg/l.  NOEL (2 y) for rats 100 ppm (0.5 mg/kg b.w. daily).  ADI 0.005 mg/kg.  Other Non-teratogenic in rats and rabbits. Non-genotoxic as demonstrated in vivo.

ECOTOXICOLOGY
Birds Dietary LC₅₀ for bobwhite quail and mallard ducks >5620 mg/kg.  Fish LC₅₀ (96 h) for rainbow trout 227, mirror carp 240 mg/l.  Daphnia LC₅₀ (48 h) >200 mg/l.  Algae EC₅₀ (96 h) for Selenastrum capricornutum 1.2 mg/l.  Bees Low toxicity to bees, both by topical and oral application; LD₅₀ >200 mg/bee.  Worms LC₅₀ (14 d) >1000 mg/kg soil.

ENVIRONMENTAL FATE
Animals Rapidly excreted in the urine, the major metabolite being 4-hydroxysulcotrione.  Plants Deactivated by the formation of 2-chloro-4-methylsulfonylbenzoic acid.  Soil/Environment Rapidly degraded in soil; lab. DT₅₀ 15-74 d; field DT₅₀ 1-11 d. The major metabolite is 2-chloro-4-methylsulfonylbenzoic acid. K_oc 44 (high pH, sandy clay loam) to 940 (low pH sand). No adverse effects on soil micro-organisms.