Common name: Paclobutrazol
IUPAC name: (2RS,3RS)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1H-1,2,4-triazol-1-yl)pentan-3-ol
Chemical Abstracts name:
(R*,R*)-(±-b-[(4-chlorophenyl)methyl]-a-(1,1-dimethylethyl)-1H-1,2,4-triazole-1-ethanol
CAS RN:[76738-62-0]
PHYSICAL CHEMISTRY
Mol. wt.: 293.8
Form:White, crystalline solid.
M.p.: 165-166 ºC
V.p.: 0.001 mPa (20 ºC)
Kow logP= 3.2
Henry:1.13×10-5 Pa m3 mol-1 (calc.)
S.g./density: 1.22 g/ml
Solubility In water 26 mg/l (20 ºC). In acetone 110, cyclohexanone 180, dichloromethane 100, hexane 10, xylene 60, methanol 150, propylene glycol 50 (all in g/l, 20 ºC).
Stability Stable for more than 2 years at 20 ºC, and more than 6 months at 50 ºC. Stable to hydrolysis (pH 4-9), and not degraded by u.v. light (pH 7, 10 days).
TOXICOLOGY
Oral Acute oral LD50 for male rats 2000, female rats 1300, male mice 490, female mice 1200, guinea pigs 400-600, male rabbits 840, female rabbits 940 mg/kg.
Skin and eye Acute percutaneous LD50 for rats and rabbits >1000 mg/kg. Mild skin irritant; moderate eye irritant (rabbits). Not a skin sensitiser (guinea pigs).
Inhalation LC50 (4 h) for male rats 4.79, female rats 3.13 mg/l air.
NOEL (1 y) for dogs 75 mg/kg daily; (2 y) for rats 250 mg/kg diet.
ADI (JMPR) 0.1 mg/kg b.w. Other Not mutagenic
Toxicity class WHO (a.i.) III
EPA (formulation) IV
EC hazard (Xn; R20/22| R36| N; R51, R53)
ECOTOXICOLOGY
Birds Acute oral LD50 for mallard ducks >7900 mg/kg.
Fish LC50 (96 h) for rainbow trout 27.8 mg/l. NOEC 3.3 mg/l.
Daphnia LC50 (48 h) 33.2 mg/l.
Algae EC50 (cell volume) for Chlorella fusca 180 mmol/l
Bees Acute oral NOEL >0.002 mg/bee; acute percutaneous NOEL >0.040 mg/bee.
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