Common name: quinclorac
IUPAC name: 3,7-dichloroquinoline-8-carboxylic acid
Chemical Abstracts name: 3,7-dichloro-8-quinolinecarboxylic acid
CAS RN: [84087-01-4]
PHYSICAL CHEMISTRY
Mol. wt.: 242.1; M.f.: C10H5Cl2NO2 Form: Colourless crystals. M.p.: 274 ºC; V.p.: <0.01 mPa (20 ºC). KOW: logP = -1.15 (pH 7). Henry: <3.72x10-2 Pa m3 mol-1 (calc.) S.g./density: 1.75; Solubility: In water 0.065 mg/kg (pH 7, 20 ºC). In ethanol, acetone 2 g/kg (20 ºC). Practically insoluble in other organic solvents. Stability: Stable to heat and light and between pH 3 to 9. pKa 4.34 (20 ºC).
APPLICATIONS
Biochemistry: Synthetic auxin (acting like indolylacetic acid); also inhibitor of cell wall (cellulose) biosynthesis.
Mode of action: Rapidly absorbed through the foliage. Weak auxin activity as determined in wheat coleoptile elongation test, cucumber root elongation test, cucumber curvature test and ethylene biosynthesis test in soya beans. No influence on Hill reaction. Plant response is similar to IAA or auxin-type herbicides of the class of benzoic acids and pyridine compounds.
Uses: Pre- and post-emergence control of grass weeds (Echinochloa spp., Aeschynomene spp., Sesbania spp.) and other weeds in direct-seeded and transplanted rice, at 0.25-0.75 kg a.i./ha.
Phytotoxicity: Non-phytotoxic to transplanted and direct-seeded rice. Under continuous irrigation conditions, injury may occur in adjacent umbelliferous crops if connected to the same waterway.
Formulation types: GR; SC; WP.
Compatibility: Good combination partner for all rice herbicides which are insufficiently effective against Echinochloa.
MAMMALIAN TOXICOLOGY
Oral: Acute oral LD50 for rats 2680, mice >5000 mg/kg.
Skin and eye: Acute percutaneous LD50 for rats >2000 mg/kg. Non-irritating to eyes and skin (rabbits).
Inhalation: LC50 (4 h) for rats >5.2 mg/l.
NOEL: (2 y) for rats 533 mg/kg b.w.
Other: Not carcinogenic.
Toxicity class: WHO (a.i.) III (Table 5); EPA (formulation) III
EC hazard: Xi; R43
ECOTOXICOLOGY
Birds: Acute oral LD50 for mallard ducks and quail >2000 mg/kg. Dietary LD50 (8 d) for mallard ducks >5000 mg/kg.
Fish: LC50 (96 h) for rainbow trout, bluegill sunfish, carp, and minnows >100 mg/l.
Daphnia: LC50 (48 h) 113 mg/l.
Other aquatic spp.: LC50 (96 h) for mysid shrimp (Mysidopsis bahia) 67, blue crab >100 mg/l. LC50 (48 h) for Quahog clam >100 mg/l.
Bees: Non-toxic by contact or ingestion.
ENVIRONMENTAL FATE
Animals: More than 90% of radiolabelled quinclorac administered orally to rats is excreted in the urine within 5 days.
Plants: In plants, systematically translocated to the roots and to the leaves.
Soil/Environment: Only slightly adsorbed by the soil. Depending on soil type and organic matter content, the chemical is relatively mobile, this mobility increasing with higher percolation rates in fields. Quinclorac is degraded by micro-organisms, 3-chloro-8-quinolinecarboxylic acid being a major metabolite. Water regimes causing changes in moisture content in rice soils enhance the microbial degradation. Photolytic decomposition in active paddy water occurs in the presence of sunlight and dissolved humic acids.
