Dithianon

NOMENCLATURE
Common name dithianon (BSI, E-ISO, (m) F-ISO, JMAF); no name (Italy) IUPAC name 5,10-dihydro-5,10-dioxonaphtho[2,3-b]-1,4-dithiine-2,3-dicarbonitrile; 2,3-dicyano-1,4-dithia-anthraquinone
Chemical Abstracts name 5,10-dihydro-5,10-dioxonaphtho[2,3-b]-1,4-dithi-in-2,3-dicarbonitrile CAS RN [3347–22–6] EC no. 222–098–6
PHYSICAL CHEMISTRY
Mol. wt. 296.3 M.f. C₁₄H₄N₂O₂S₂ Form Dark brown crystals, with a coppery lustre; (tech., lighter brown). M.p. 215–216 °C V.p. 2.7 × 10^-6 mPa (25 °C) K_ow logP = 3.2 Henry 5.47 × 10^-6 Pa m³ mol^-1 (calc.) S.g./density 1576 kg/m³ (20 °C) Solubility In water 0.14 mg/l (pH 7, 20 °C). In chloroform 12, acetone 10, benzene 8 (all in g/l, 20 °C). Sparingly soluble in methanol and dichloromethane. Stability Decomposed by alkaline media, by concentrated acids, and by prolonged heating; DT₅₀ 12.2 h (pH 7, 25 °C). Stable up to 80 °C. Aqueous solution (0.1 mg/l) exposed to artificial sunlight had DT₅₀ 19 h.
APPLICATIONS
Biochemistry Affects a range of fungal enzymes by reacting with thiol groups and interfering with cellular respiration. Multi-site mode of action. Mode of action Foliar fungicide with protective and, to some extent, curative action. Uses Control of many foliar diseases (but not powdery mildews), including scab, on pome fruit; Stigmina carpophila, Plasmopara viticola hiemalis and scab on cherries; monilia spp., rust and leaf curl on peaches and apricots; leaf spot and rust on currants; Didymella applanata on raspberries; Mycosphaerella fragariae and Diplocarpon earliana on strawberries; Plasmopara viticola on vines; downy mildew on hops; scab and Phomopsis citri on citrus fruit; Ascochyta chrysanthemi on chrysanthemums under glass; G lomerella cingulata on coffee; Marssonina leaf spot on poplars; etc. Applied at 1400 g/ha (hops), 525 g/ha (pome and stone fruit), 560 g/ha (vines). Phytotoxicity Slight russetting may occur on some apple varieties, such as Golden Delicious. Formulation types SC; WG; WP. Compatibility Incompatible with petroleum oils, alkaline materials, and sulfur-containing compounds.  
ENVIRONMENTAL FATE
Animals Dithianon was detected in only trace amounts in tissues and/or excreta. It is rapidly and intensively metabolised by a number of degradation processes; the key degradation steps are assumed to be oxidation/reduction and reaction with nucleophiles, commonly thiols, in the form of proteins and peptides such as glutathione. These reactions result in a huge number of individual metabolites. No individual metabolite has been identified; all were present in minor amounts. Plants Dithianon was identified as the major component of the residue in all plants/plant parts investigated.The parent compound is further metabolised to a large number of polar, minor unidentified components. Soil/Environment Soil DT₅₀ (lab, 20 °C, 41–45% MWHC) 2.6–37.6 d; soil DT₉₀ (lab, 20 °C; 41-45% MWHC) 8.5–125 d; Water DT₅₀ (pH 7, 20°C) 0.6 d; K_oc 1167–6004 ml/g; air DT₅₀ <6.3 h.
MAMMALIAN TOXICOLOGY
Oral Acute oral LD₅₀ for rats >300 mg/kg b.w. Skin and eye Acute percutaneous LD₅₀ for rats >2000 mg/kg b.w. No skin irritation; severe eye irritant. Inhalation LC₅₀ (4 h) for male rats 0.28 mg/l air. NOEL (2 y) for rats 1 mg/kg b.w./day, (1 y) for dogs 1.6 mg/kg/b.w./day; (18 mo) for mice 2.8 mg/kg b.w../day. ADI (JMPR) 0.01 mg/kg b.w. [2010]. Other Not genotoxic in vivo. Toxicity class WHO (a.i.) II (acute oral); III (acute dermal). EPA (formulation) Mild acute oral toxicity, no specific reproductive or developmental toxicity, no concern for carcinogenicity (rare tumors in female rat kidney most probably due to sustained cytotoxicity; not genotoxic). EC classification Xn; R22| N; R50, R53. (T; R22, R23, R41, R43| N; R50, R53).
ECOTOXICOLOGY
Birds Acute oral LD₅₀ for quail (Colinus virginianus) 309, for duck (Anas platyrhynchos) >2000 mg/kg b.w./day. Short-term dietary toxicity LC₅₀ for quail >5200, for duck >5000 mg/kg feed. Fish LC₅₀ (96 h) for trout (Oncorhynchus mykiss) 44 μg/l. Daphnia EC₅₀ (48 h) 260 μg/l. Algae EC₅₀ (72 h) for Selenastrum capricomutum 90 μg/l. Other aquatic spp. NOEC (28 d) for Chironomus riparius 125μg/l. Bees Contact LD₅₀ >0.1 mg/bee. Worms LC₅₀ (14 d) 578.4 mg/kg soil. Other beneficial spp. No risk or unacceptable effects anticipated for non-target arthropods.