NOMENCLATURE
Common name fenclorim (BSI, draft E-ISO); fenclorime ((f) draft F-ISO)
IUPAC name 4,6-dichloro-2-phenylpyrimidine
Chemical Abstracts name 4,6-dichloro-2-phenylpyrimidine
CAS RN [3740-92-9] Development codes CGA 123 407 (Ciba-Geigy)

PHYSICAL CHEMISTRY
Mol. wt. 225.1 M.f. C10H6Cl2N2 Form Colourless crystals. M.p. 96.9 oC V.p. 12 mPa (20 oC) KOW logP = 4.17 Henry 1.1 Pa m3 mol-1 (calc.) S.g./density 1.5 g/cm3 (20 oC) Solubility In water 2.5 mg/l (20 oC). In acetone 14%, cyclohexanone 28%, dichloromethane 40%, toluene 35%, xylene 30%, hexane 4%, methanol 1.9%, n-octanol 4.2%, and isopropanol 1.8%. Stability Stable in neutral, acidic and weakly alkaline media. Stable up to 400 oC.

COMMERCIALISATION
History Herbicide safener reported by J. Rufener & M. Quadranti (Proc. 10th Int. Congr. Plant Prot., 1983, 1, 332). Introduced by Ciba-Geigy Ltd (now Syngenta AG). Patents EP 55693; US 4493726 Manufacturers Syngenta

APPLICATIONS
Biochemistry Fenclorim influences the metabolism of pretilachlor in rice, which proceeds via glutathione conjugation. Mode of action Herbicide safener. Taken up rapidly by the roots of germinating rice seeds, and protects them from potential damage caused by pretilachlor. Uses Used as a safener for pretilachlor in direct-seeded rice. Formulation types EC. Selected tradenames: mixtures: 'Sofit' (+ pretilachlor) (direct-sown rice) (Syngenta)

ANALYSIS
Residues determined by glc.

MAMMALIAN TOXICOLOGY
Oral Acute oral LD50 for rats >5000 mg/kg. Skin and eye Acute percutaneous LD50 for rats >2000 mg/kg. Non-irritating to skin and eyes (rabbits). Sensitising to skin (guinea pigs). Inhalation LC50 (4 h) for rats 2.9 mg/l air. NOEL (2 y) for rats 10.4, mice 113 mg/kg b.w. daily; (1 y) for dogs 10.0 mg/kg b.w. daily; (90 d) for rats 100 mg/kg b.w. daily. Toxicity class WHO (a.i.) III (Table 5) EC hazard (R20; R43)

ECOTOXICOLOGY
Birds Acute oral LD50 for Japanese quail >500 mg/kg. LC50 for Japanese quail >10 000 ppm. Fish LC50 (96 h) for rainbow trout 0.6, catfish 1.5 mg/l. Daphnia LC50 (48 h) 2.2 ppm. Algae IC50 (5 d) for Scenedesmus subspicatus 20.9 ppm. Bees Non-toxic to honeybees; LD50 (ingestion) >20 mg/bee; (contact) >1000 ppm. Worms LC50 (14 d) for earthworms >62.5 mg/kg.

ENVIRONMENTAL FATE
Animals Rapidly absorbed, metabolised to polar compounds and excreted. No accumulation of residues in tissues. Plants Readily metabolised to polar compounds. At harvest time, residues are negligible. Soil/Environment In soil, DT50 17-35 d. Fenclorim and its metabolites are strongly adsorbed onto soil.