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

solubility 

Chloroform (Slightly), Methanol (Slightly)

pka

13.06±0.46(Predicted)

form 

solid

Water Solubility 

Soluble

BRN 

8415832

Exposure limits

OSHA PEL: TWA 0.25 mg/m3; ACGIH TLV: TWA 0.25 mg/m3.

Stability:

Temperature Sensitive

NIST Chemistry Reference

Monocrotophos(6923-22-4)

EPA Substance Registry System

Monocrotophos (6923-22-4)

Safety Information

Hazard Codes 

T+;N,N,T+,Xn,F

Risk Statements 

24-26/28-50/53-68-67-65-38-11-36-20/21/22

Safety Statements 

1/2-36/37-45-60-61-62-26-16

RIDADR 

UN 2783

OEB

C

OEL

TWA: 0.25 mg/m3

WGK Germany 

3

RTECS 

TC4375000

HazardClass 

6.1(a)

PackingGroup 

II

HS Code 

29241200

Hazardous Substances Data

6923-22-4(Hazardous Substances Data)

Toxicity

LD50 in male, female rats (mg/kg): 17, 20 orally; 126, 112 dermally (Gaines)

Monocrotophos Usage And Synthesis

Description

Monocrotophos is a colorless to reddish-brownsolid with a mild ester odor. Molecular weight = 223.19;Specific gravity (H2O:1)= 13; Boiling point= 125℃; Freezing/Melting point = 53.9℃ (pure); 25- -30℃ (thereddish brown technical product); Vapor pressure =7X10-mm at 20^C; Flash point= >93*C. HazardIdentification (based on NFPA-704 M Rating System):Health 3, Flammability 1, Reactivity 0. Soluble in water.Commercially available as a water-miscible solution.

Chemical Properties

Monocrotophos is a colorless to reddishbrown solid with a mild ester odor.

Uses

Monocrotophos 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.

Uses

Systemic 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.

Uses

Monocrotophos is used to control a wide spectrum of chewing and sucking insects and also mites in a large variety of crops, especially cotton.

Definition

ChEBI: An alkenyl phosphate that is the 4-(methylamino)-4-oxobut-2-en-2-yl ester of dimethyl phosphate.

General Description

Colorless 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 Reactions

Water soluble. Rapidly hydrolyzed.

Reactivity Profile

Monocrotophos 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.

Hazard

Flammable, dangerous fire risk. Use may be restricted. Toxic via ingestion, inhala- tion, and skin absorption. Questionable carcinogen. Cholinesterase inhibitor.

Health Hazard

Extremely 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 Hazard

Monocrotophos 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 Hazard

Wear 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 Profile

Poison 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 Exposure

The liquid form is a severely hazardous pesticide formulation. A potential danger to those involved in the manufacture, formulation, and application of this insecticide.

First aid

If this chemical gets into the eyes, remove anycontact lenses at once and irrigate immediately for at least15 min, occasionally lifting upper and lower lids. Seek medical attention immediately. If this chemical contacts theskin, remove contaminated clothing and wash immediatelywith soap and water. Speed in removing material from skinis of extreme importance. Shampoo hair promptly if contaminated. Seek medical attention immediately. If thischemical has been inhaled, remove from exposure, beginrescue breathing (using universal precautions, includingresuscitation mask) if breathing has stopped and CPR ifheart action has stopped. Transfer promptly to a medicalfacility. When this chemical has been swallowed, get medical attention. Give large quantities of water and inducevomiting. Do not make an unconscious person vomit.Obtain authorization and/or further instructions from thelocal hospital for administration of an antidote or performance of other invasive procedures.

Environmental Fate

Plant. 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 pathway

Technical 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 K_ow. 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.

storage

Color Code—Blue: Health Hazard/Poison: Storein a secure poison location. Prior to working with thischemical you should be trained on its proper handling andstorage. Store in tightly closed containers in a cool, wellventilated area. Sources of ignition, such as smoking andopen flames, are prohibited where this chemical is handled,used, or stored. Metal containers involving the transfer of 5gallons or more of this chemical should be grounded andbonded. Drums must be equipped with self-closing valves,pressure vacuum bungs, and flame arresters. Use only nonsparking tools and equipment, especially when opening andclosing containers of this chemical. Wherever this chemicalis used, handled, manufactured, or stored, use explosionproof electrical equipment and fittings

Shipping

UN2783 Organophosphorus pesticides, solid, toxic, Hazard Class: 6.1; Labels: 6.1-Poisonous materials.

Degradation

Monocrotophos 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).

Incompatibilities

Alkaline pesticides. Attacks black iron, drum steel; stainless steel; brass.

Waste Disposal

Small 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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