Cyazofamid

Common name cyazofamid (BSI, E-ISO); cyazofamide ((m) F-ISO)

 

IUPAC name 4-chloro-2-cyano-N,N-dimethyl-5-p-tolylimidazole-1-sulfonamide

Chemical Abstracts name 4-chloro-2-cyano-N,N-dimethyl-5-(4-methylphenyl)-1H-imidazole-1-sulfonamide CAS RN [120116–88–3] Development codes IKF-916 (Ishihara Sangyo) Smiles code CN(C)S(=O)(=O)n1c(C#N)nc(Cl)c1c2ccc(C)cc2

PHYSICAL CHEMISTRY

Composition Tech is ≥93.5% pure.

Mol. wt. 324.8 M.f. C₁₃H₁₃ClN₄O₂S Form Ivory, odourless powder. M.p. 152.7 °C V.p. <1.3 × 10^-2 mPa (35 °C) K_ow logP = 3.2 (25 °C) Henry <4.03 × 10^-2 Pa m³ mol^-1 (20 °C, calc.) S.g./density 1.446 (20 °C) Solubility In water 0.121 (pH 5), 0.107 (pH 7), 0.109 (pH 9) (all in ppm, 20 °C). In acetone 41.9, toluene 5.3, dichloromethane 101.8, hexane 0.03, ethanol 1.54, ethyl acetate 15.63, octanol 0.25, acetonitrile 29.4, isopropanol 0.39 (all in g/l, 20 °C). Stability In water DT₅₀ 24.6 d (pH 4), 27.2 d (pH 5), 24.8 d (pH 7).

APPLICATIONS

Biochemistry ‘Quinone inside Inhibitor’. Both cyazofamid and the strobilurin fungicides inhibit at complex III (ubiquinol-cytochrome c reductase) in the mitochondrial respiratory chain. However, cyazofamid inhibits Qi (the ubiquinone reducing site) of cytochrome bc1, whereas the strobilurins inhibit Qo (the ubiquinol oxidising site) of cytochrome bc1. Selectivity appears to be due to a difference in the susceptibility of the target enzyme_. Mode of action Foliar and soil preventive fungicide with residual activity and rainfastness, together with moderate translaminar and curative activity. Inhibits all stages in the lifecycle of Phytophthora infestans.

Uses For control of Oomycete and Plasmodiophora diseases, such as potato and tomato late blight (Phytophthora infestans) and downy mildews (e.g. Pseudoperonospora cubensis of cucumber), at 60–100 g/ha. Its use as a foliar treatment on other crops, such as vines, onions, lettuce, rice and crucifers, is under investigation.

Formulation types SC.

TOXICOLOGICAL & ENVIRONMENTAL REVIEWS

EU Rev. Rep. SANCO/10379/2002, Nov. 2002. EPA Fact Sheet, Sep. 2004. FSC Eval. Rep., 2004. 91/414/EC Annex I status Included, 2003/23/EC.

MAMMALIAN TOXICOLOGY

Oral Acute oral LD₅₀ for rats and mice >5000 mg/kg. Skin and eye Acute percutaneous LD₅₀ for rats >2000 mg/kg. Not irritating to eyes or skin (rabbits). Not a skin sensitiser (guinea pigs). Inhalation LC₅₀ for rats >5.5 mg/l. NOEL NOAEL for male rats 500 ppm (17 mg/kg b.w. daily). ADI/RfD (EC) 0.17 mg/kg b.w. [2003]; (EPA) aRfD 1.0, cRfD 0.95 mg/kg b.w. [2004]; (FSC) 0.17 mg/kg b.w. [2004] Other Negative in Ames, REC assay, chromosomal aberration and mouse micronucleus tests.

ECOTOXICOLOGY

Birds Acute oral LD₅₀ for quail and ducks >2000 mg/kg. Dietary LC₅₀ for quail and ducks >5000 ppm (EU Rev. Rep.). Fish LC₅₀ (96 h) for rainbow trout >0.510, carp >0.14 mg/l (both the highest achievable concentration in water). Daphnia EC₅₀ (48 h) >0.14 mg/l (highest achievable concentration in water). Algae E_bC₅₀ (72 h) for Selenastrum capricornutum 0.025 mg/l. Bees LD₅₀ for honeybees (oral) >151.7 μg/bee; (contact) >100 μg/bee. Worms Acute LC₅₀ (14 d) for earthworms >1000 mg/kg. Other beneficial spp. Harmless to Aphidius rhopalosiphi, Typhlodromus pyri, Chrysoperla carnea and Aleochara bilineata (IOBC).

ENVIRONMENTAL FATE

Animals Rapidly absorbed, with 90% excreted within 24 h in faeces and in urine. Excreted material was mainly unchanged cyazofamid and 4-(4-chloro-2-cyanoimidazol-5-yl)benzoic acid (EU Rev. Rep., EPA Fact Sheet, FSC Eval. Rep.). Plants Cyazofamid is poorly absorbed from soil or foliar application (tomatoes). The main residue component is unchanged parent. (FSC Eval. Rep.). Soil/Environment Rapidly degraded in soil, DT₅₀ 3–5 d; the main end metabolite is 4-chloro-5-p-tolylimidazole-2-carboxylic acid. DT₅₀ for aerobic aquatic metabolism c. 10–18 d; 4-chloro-5-p-tolylimidazole-2-carbonitrile is the major degradate. Soil K_oc 736–2172 (EPA Fact Sheet).