Herbicide
HRAC  B WSSA  2; pyrimidinyloxybenzoic



NOMENCLATURE
Common name bispyribac-sodium (BSI, pa ISO)
IUPAC name sodium 2,6-bis(4,6-dimethoxypyrimidin-2-yloxy)benzoate 
Chemical Abstracts name sodium 2,6-bis[(4,6-dimethoxy-2-pyrimidinyl)oxy]benzoate 
CAS RN [125401-75-4] for acid; [125401-92-5] for sodium salt  Development codes KIH-2023; KUH-911 (both Kumiai); V-10029

PHYSICAL CHEMISTRY
Composition Tech. is >93%.  Mol. wt. 452.4  M.f. C₁₉H₁₇N₄NaO₈; C₁₉H₁₈N₄O₈ for the acid  Form White powder.  M.p. 223-224 °C  V.p. 5.05 ×10^-6 mPa (25 ºC)  K_OW logP = -1.03 (23 °C)  Henry 3.12 × 10^-11 Pa m³ mol^-1 (calc.)  S.g./density Bulk density 0.0737 (20 °C, CIPAC MT 3)  Solubility In water 73.3 g/l (25 ºC). In methanol 26.3, acetone 0.043 g/l (25 °C).  Stability Stable in water; DT₅₀ >1 y (pH 7 & 9), 448 h (pH 4). Stable to light. Not decomposed after 14 d at 55 °C.  pKa 3.05

APPLICATIONS
Biochemistry Branched chain amino acid synthesis (ALS or AHAS) inhibitor.  Mode of action Selective, systemic post-emergence herbicide, absorbed by foliage and roots.  Uses Control of grasses, sedges and broad-leaved weeds, especially Echinochloa spp., in direct-seeded rice, at rates of 15-45 g/ha. Also used to stunt growth of weeds in non-crop situations.  Formulation types SC; water-soluble liquid.

ANALYSIS
By hplc. Details available from Kumiai.

MAMMALIAN TOXICOLOGY
Oral Acute oral LD₅₀ for male rats 4111, female rats 2635, male and female mice 3524 mg/kg.  Skin and eye Acute percutaneous LD₅₀ for rats >2000 mg/kg. Non-irritating to skin; slightly irritating to eyes (rabbits).  Inhalation LC₅₀ (4 h) for rats >4.48 mg/l.  NOEL (2 y) for male rats 20 mg/kg diet (1.1 mg/kg b.w. daily), female rats 20 mg/kg diet (1.4 mg/kg b.w. daily), male mice 14.1 mg/kg daily, female mice 1.7 mg/kg b.w. daily.  ADI 0.011 mg/kg.  Other Non-mutagenic in the Ames test, and non-teratogenic to rats and rabbits.  Toxicity class WHO (a.i.) III (Table 5)

ECOTOXICOLOGY
Birds Acute oral LD₅₀ for bobwhite quail >2250 mg/kg. Dietary LC₅₀ (5 d) for bobwhite quail and mallard ducks >5620 mg/kg diet.  Fish Acute LC₅₀ (96 h) for rainbow trout and bluegill sunfish >100 ppm.  Daphnia LC₅₀ (48 h) >100 ppm.  Algae EC₅₀ (120 h) for Selenastrum capricornutum 3.4 mg/l, NOEC 0.625 mg/l.  Bees LD₅₀ (oral) >200 mg/bee; LC₅₀ (contact) >7000 mg/l spray.  Worms NOEL (14 d) for Eisenia foetida >1000 mg/kg soil.

ENVIRONMENTAL FATE
Animals >95% of dose applied to rats was excreted in urine and faeces within 7 d.  Plants Following application to foliage and soil at 5-leaf stage of rice plants, c. 10% of carbon label was distributed between straw and roots at harvest.  Soil/Environment In soil, DT₅₀ <10 d (flooded and upland conditions).