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Monocrotophos

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Monocrotophos Basic information
Monocrotophos Chemical Properties
  • Melting point:54-55°C
  • Boiling point:125°C (0.0005 torr)
  • Density 1.3300
  • vapor pressure 2.9×10-4 Pa (20 °C)
  • Flash point:-18 °C
  • storage temp.  0-6°C
  • pka13.06±0.46(Predicted)
  • form solid
  • Water Solubility Soluble
  • BRN 8415832
  • Exposure limitsOSHA PEL: TWA 0.25 mg/m3; ACGIH TLV: TWA 0.25 mg/m3.
  • NIST Chemistry ReferenceMonocrotophos(6923-22-4)
  • EPA Substance Registry SystemMonocrotophos (6923-22-4)
Safety Information
Monocrotophos Usage And Synthesis
  • Chemical PropertiesMonocrotophos is a colorless to reddishbrown solid with a mild ester odor.
  • UsesSystemic insecticide and acaricide used to control pests in cotton, sugarcane, coffee, tobacco, olives, rice, hops, sorghum, maize, deciduous fruits, citrus fruits, potatoes, sugarbeet, tomatoes, soya beans and ornamentals.
  • UsesMonocrotophos is an organophosphorous insecticide. Monocrotophos is used mainly against cotton pests but it is also used in the protection of citrus, rice, potatoes, vegetables and other crops.
  • UsesInsecticide.
  • UsesMonocrotophos is used to control a wide spectrum of chewing and sucking insects and also mites in a large variety of crops, especially cotton.
  • DefinitionChEBI: An alkenyl phosphate that is the 4-(methylamino)-4-oxobut-2-en-2-yl ester of dimethyl phosphate.
  • General DescriptionColorless crystals with a mild ester odor, commercial product is a reddish-brown solid. Used as a fast acting insecticide with both systemic and contact action against a wide range of pests on cotton, sugar cane, tobacco, potatoes, peanuts, tomatoes, and ornamentals. Very toxic.
  • Air & Water ReactionsWater soluble. Rapidly hydrolyzed.
  • Reactivity ProfileMonocrotophos is incompatible with the following: Metals, low molecular weight alcohols & glycols [Note: Corrosive to black iron, drum steel, stainless steel 304 & brass. Should be stored at 70-80°F.] . Incompatible with alkaline compounds.
  • HazardFlammable, dangerous fire risk. Use may be restricted. Toxic via ingestion, inhala- tion, and skin absorption. Questionable carcinogen. Cholinesterase inhibitor.
  • Health HazardExtremely toxic phosphate ester; however,susceptible to hydrolyze in acid or alkali;cholinesterase inhibitor; toxic properties aresimilar to those of dicrotophos, symptomsinclude headache, dizziness, pinpoint pupils,blurred vision, weakness, muscle spasms,vomiting, diarrhea, abdominal cramp, short-ness of breath, and hypotension; high expo-sure may cause seizure, coma, and respiratoryparalysis.
    LD50 oral (rat): 8 mg/kg
    LD50 oral (mouse): 15 mg/kg
    LD50 skin (rat): 112 mg/kg
    LC50 inhalation (rat): 63 mg/m3 /4 h.
  • Health HazardMonocrotophos is an organophosphorus pesticide. It is a cholinesterase inhibitor and acts on the nervous system. Extremely toxic; probable oral lethal dose to humans 5-50 mg/kg or between 7 drops and 1 teaspoon for a 70 kg (150 lb.) person. Repeated inhalation or skin contact with Monocrotophos may, without symptoms, progressively increase susceptibility to poisoning.
  • Fire HazardWear positive pressure breathing apparatus and full protective clothing. Container may explode in heat of fire. Toxic fumes evolved when heated to decomposition. Incompatible with alkaline compounds. Unstable in aqueous solution above pH 7.0; in low molecular weight alcohols and glycols. Stable in ketones and higher molecular weight alcohols and glycols. Stable when stored in glass or polyethylene containers. Relatively stable in sunlight. Keep away from temperatures above 80F; do not store below 70F. Corrosive to black iron, drum steel, stainless steel 304 and brass, but not to glass, aluminum, or stainless steel 316.
  • Safety ProfilePoison by ingestion, inhalation, skin contact, intraperitoneal, subcutaneous, and intravenous routes. Mutation data reported. Use may be restricted. When heated to decomposition it emits very toxic NOx and POx.
  • Potential ExposureThe liquid form is a severely hazardous pesticide formulation. A potential danger to those involved in the manufacture, formulation, and application of this insecticide.
  • Environmental FatePlant. Decomposes in plants forming the N-hydroxy compound in small amounts (Hartley and Kidd, 1987).
    Chemical/Physical. Hua et al. (1995) studied the titanium dioxide-mediated photooxidation of monocrotophos using a recirculating photoreactor. The initial concentration and flow rate used were 50 nM and 30 mL/minute, respectively. The irradiation
    Emits toxic fumes of phosphorus and nitrogen oxides when heated to decomposition (Sax and Lewis, 1987; Lewis, 1990).
  • Metabolic pathwayTechnical monocrotophos contains 75-80% of the Ε-isomer and 9% of the 2-isomer, the balance being various impurities. Most studies on the metabolic fate of this compound have used purified material containing >99% E-isomer. Monocrotophos is a systemic vinyl phosphate insecticide with a particularly high water solubility and low log Kow. This hydrophilic property influences its metabolism and environmental fate in that it tends to remain in the water phase and does not bioaccumulate.
    The main routes of metabolic degradation are demethylation to des- O-methylmonocrotophos and hydrolysis to dimethylphosphate and N-methylacetoacetamide. Hydroxylation of the N-methyl group in animals and plants followed by N-demethylation are also important from a toxicological points of view, since these metabolic steps yield active acetylcholinesterase inhibitors.
  • ShippingUN2783 Organophosphorus pesticides, solid, toxic, Hazard Class: 6.1; Labels: 6.1-Poisonous materials.
  • DegradationMonocrotophos is thermally labile, decomposing exothermically at >55°C (PM). This thermo-instability has been known to cause manufacturing problems. It is relatively stable at acidic and neutral pH values but it is hydrolysed in alkaline solutions (PM). The DT50s at pH 3, 6 and 9 were 131, 134 and 26 days, respectively. Products of hydrolysis were N-methylacetoacetamide (2), the main product at alkaline pH values, and O-desmethylmonocrotophos (3), which predominated in acid and neutral solutions (Lee et al., 1990). Further decomposition of N-methylacetoacetamide (2) then gave acetone (4), CO2 and methylamine (5), whereas under acidic conditions the O-desmethylmonocrotophos was shown to decompose to inorganic phosphate (6), monomethyl phosphate (7), methanol (B), acetone (4) and N-methylacetoacetamide (2) (Beynon et al., 1973).
    Since monocrotophos does not significantly absorb light at wavelengths greater than 300 nm, little photolysis would be expected to take place in sunlight. Photolysis experiments in which aqueous solutions of monocrotophos were exposed to sunlight in quartz tubes showed no products other than the hydrolysis products 2 and 3, neither was their rate of production accelerated. A soil surface photolysis experiment indicated loss of monocrotophos, probably as CO2, due to microbial action. No particular photolytic degradation products were detected apart from minor amounts of the hydrolytic products 2 and 3 (Lee et al., 1990) (see Scheme 1).
  • IncompatibilitiesAlkaline pesticides. Attacks black iron, drum steel; stainless steel; brass.
  • Waste DisposalSmall amounts may be hydrolyzed with water. Incineration in a unit with effluent gas scrubbing is recommended for larger amounts. In accordance with 40CFR165, follow recommendations for the disposal of pesticides and pesticide containers. Must be disposed properly by following package label directions or by contacting your local or federal environmental control agency, or by contacting your regional EPA office.
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