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Physical Properties
Molecular weight:228.7; Physical form:Colourless crystals; ( tech., beige to brown flakes). Density:1.233 g/cm3 (22 °C); Composition:Tech. grade is c. 92% pure. Melting point:101 °C; ( tech., 95-100 °C); Vapour pressure:5.77 ×10-2 mPa (20 °C); 9.83 × 10-2 mPa (25 °C); Henry constant:5.28 × 10-4 Pa m3 mol-1 ( calc.); Partition coefficient(n-octanol and water):logP >2.37 ( pH 5), = 1.32 ( pH 7), = -0.17 ( pH 9); pKa:4.84; Solubility:In water 0.11 ( pH 5), 4.4 ( pH 7), 444 ( pH 9) (all in g/l, 20 °C). In acetone 313, dichloromethane 169, ethanol 150, hexane 0.26, toluene 8 (all in g/l, room temperature). The common alkali-metal and amine; Stability:The acid is chemically very stable. Stable to hydrolysis at pH 5-9 (25 °C). The solid is stable to sunlight; solutions degrade, DT50 2.2 d. Stable to aluminium, tin and iron up to 150 °C. Forms water-soluble alk;
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Toxicology
Oral:Acute oral LD50 for rats 4700 mg/ kg. Percutaneous:Acute percutaneous LD50 for rats >2000 mg/kg. Oral LD50 800 mg/kg.Eye irritant; not a skin irritant. Not a skin sensitiser. Inhalation: LC50 (4 h) for rats >1.14 mg/l air.
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Environmental Profile
Ecotoxicology:
Bees:Not toxic to bees.Birds: LC50 for birds >20 000 mg/ kg.Fish: LC50 (48 h) for rainbow trout 75, fathead minnows 11 mg/l.
Environmental fate:
Animals:Studies in cattle show that MCPB is excreted in the urine, either unchanged or as MCPA. Levels in milk were at or below the method level of detection.Soil:In soil, metabolism involves degradation of the side-chain to 4-chloro-2-methylphenol, ring hydroxylation, and ring opening. Duration of residual activity in soil is c. 6 w. DT50 c. 5-7 d (5 soil types, Plant:In susceptible plants, undergoes b-oxidation to MCPA, which is subsequently degraded to 4-chloro-2-methylphenol, followed by ring hydroxylation and ring opening.
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Transport Information
Signal Word:CAUTION; Hazard Class:III(Slightly hazardous)