NOMENCLATURE

Common name brodifacoum (BSI, E-ISO, (m) F-ISO, ANSI)

IUPAC name 3-[3-(4'-bromobiphenyl-4-yl)-1,2,3,4-tetrahydro-1-naphthyl]-4-hydroxycoumarin 

Chemical Abstracts name 3-[3-(4'-bromo-[1,1'-biphenyl]-4-yl)-1,2,3,4-tetrahydro-1-naphthalenyl]-4-hydroxy-2H-1-benzopyran-2-one 

CAS RN [56073-10-0] formerly [66052-95-7]  EEC no. 259-980-5  Development codes WBA 8119 (Sorex); PP581 (ICI)

PHYSICAL CHEMISTRY

Composition Tech. material is >91% pure.  Mol. wt. 523.4  M.f. C₃₁H₂₃BrO₃  Form White powder; (tech., off-white to buff or beige powder).  M.p. 228-232 ºC (tech.)  V.p. <<0.001 mPa (20 °C, gas saturation method)  K_OW logP = 8.5  Henry <10^-1 (pH 5.2); <10^-3 (pH 7.4); <10^-5 (pH 9.3) (all in Pa m³ mol^-1, calc.)  S.g./density 1.42 (25 °C, tech.)  Solubility In water 3.8 ´ 10^-3 (pH 5.2), 0.24 (pH 7.4), 10 (pH 9.3) (all in mg/l, 20 °C). In acetone 20, chloroform 3, benzene <6 (all in mg/l, 20 ºC).  Stability Thermally (up to 50 ºC) and photolytically (30 d in direct sunlight) stable. Degraded by u.v. light when in solution.  pKa A very weak acid which is too lipophilic to form water-soluble salts. 

APPLICATIONS

Biochemistry Inhibits the vitamin K-dependent steps in synthesis of clotting factors II, VII, IX and X.  Mode of action Indirect anticoagulant.  Uses Controls most rodent pests, including Rattus norvegicus, R. rattus and Mus musculus at lower rates than many other anticoagulants (e.g. warfarin and pindone); also Cricetus cricetus, Mesocricetus auratus, Microtus pennsylvanicus, M. pinetorum, R. argentiventer, R. rattus mindanensis and rodents, such as hamsters, that are difficult to control with other anticoagulants. Potency is such that a rodent may absorb a lethal dose by taking a 50 mg/kg bait as part of its food intake on only one occasion. For a review, see A. P. Buckle & R. H. Smith, "Rodent Pests and their Control", CABI (1994).  Formulation types AB; BB; RB.

ANALYSIS

Product analysis by hplc (CIPAC Handbook, 1985, 1C, 1981; AOAC Methods, 1995, 983.11; Anal. Methods Pestic. Plant Growth Regul., 1988, 16, 134). Residues determined by hplc (idem, ibid.). Details from Syngenta.

MAMMALIAN TOXICOLOGY

Oral Acute oral LD₅₀ for male rats 0.4, male rabbits 0.2, male mice 0.4, female guinea pigs 2.8, cats c. 25, dogs 0.25-3.6 mg/kg.  Skin and eye Acute percutaneous LD₅₀ for rabbits 0.25-0.63 mg/kg. Slight to mild skin and eye irritant (rabbits). A moderate skin sensitiser (guinea pigs), but negligible risk of sensitisation from formulated product.  Inhalation LC₅₀ (4 h) 5 mg/l air.  NOEL 0.02 mg/kg diet daily.  Toxicity class WHO (a.i.) Ia; EPA (formulation) I  EC hazard T+; R27/28| T; R48/24/25| N; R50, R53

ECOTOXICOLOGY

Birds Acute oral LD₅₀ for Japanese quail 11.6, chickens 4.5, mallard ducks 0.31 mg/kg. Dietary LC₅₀ (40 d) for mallard ducks 2.7, bobwhite quail 0.8 ppm.  Fish LC₅₀ (96 h) for bluegill sunfish 0.165, rainbow trout 0.051 mg/l.  Daphnia LC₅₀ (48 h) 0.34 mg a.i./l (as formulation).

ENVIRONMENTAL FATE

EHC 175 (WHO, 1995).  Animals In mammals, a number of hydroxycoumarins are formed.  Soil/Environment Degraded in soils (pH 5.5 to pH 8) under aerobic and flooded conditions. K_oc (average) 50 000, range 14 000-106 000; K_d 1040 (average), range 625-1320. DT₅₀ >12 w. Unlikely to leach; <2% leached >2 cm in laboratory columns.