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Methyl bromide

Basic information Methyl bromide fumigation methyl bromide poisoning uses Precautions Safety Related Supplier
Methyl bromide Basic information
Methyl bromide Chemical Properties
  • Melting point:−94 °C(lit.)
  • Boiling point:4 °C(lit.)
  • Density 3.3 g/mL at 25 °C(lit.)
  • vapor density 3.3 (20 °C, vs air)
  • vapor pressure 1420 mm Hg ( 20 °C)
  • refractive index 1.4432
  • Flash point:-34 °C
  • storage temp. 2-8°C
  • solubility water: soluble
  • form Colorless gas
  • explosive limit~16%
  • Water Solubility 1.522 g/100 mL
  • Merck 13,6056
  • Henry's Law Constant0.72 at 21 °C (Gan and Yates, 1996)
  • Exposure limitsNIOSH REL: IDLH 250 ppm; OSHA PEL: C 20 ppm; ACGIH TLV: TWA 5 ppm.
  • Stability:Stable. Incompatible with oxidizing agents, strong acids. This is an ozone-depleting chemical, and its use is restricted in many countries.
  • CAS DataBase Reference74-83-9(CAS DataBase Reference)
  • IARC3 (Vol. 41, Sup 7, 71) 1999
  • NIST Chemistry ReferenceMethyl bromide(74-83-9)
  • EPA Substance Registry SystemMethyl bromide (74-83-9)
Safety Information
Methyl bromide Usage And Synthesis
  • Methyl bromide fumigationMethyl bromide is used as a fumigant and pesticide. Exposure may occur during fumigation activities.
    Methyl bromide is a broad-spectrum fumigant that has been used around the world since the 1930s as a pre-plant soil fumigant to control insects, pathogens, and weeds, and to control insects in buildings and in commodities. It is also used for quarantine and pre-shipment applications.
    Methyl bromide is one of the very few chemicals that were approved for broad-spectrum use in agriculture and pest control. The dominant use of methyl bromide worldwide is for pre-planting soil fumigation.
    Methyl bromide is the most effective soil fumigant for killing plant pests, its use is being phased out because its emissions from soil can lead to stratospheric ozone depletion. 1992, Parties to the Montreal Protocol on Substances that Deplete the Ozone Layer recognized that methyl bromide has an ozone-depleting potential (ODP); thus it is identified as an ozone-depleting substance.
  • methyl bromide poisoningMethyl bromide is highly toxic. Studies in humans indicate that the lung may be severely injured by the acute (short-term) inhalation of methyl bromide. Acute and chronic (long-term) inhalation of methyl bromide can lead to neurological effects in humans. Neurological effects have also been reported in animals. Degenerative and proliferative lesions in the nasal cavity developed in rats chronically exposed to methyl bromide by inhalation. Chronic inhalation exposure of male animals has resulted in effects on the testes at high concentrations. EPA has classified methyl bromide as a Group D, not classifiable as to human carcinogenicity.
  • usesThe primary use of methyl bromide is as a fumigant in soil to control fungi, nematodes, and weeds; in space fumigation of food commodities (e.g., grains); and in storage facilities (such as mills, warehouses, vaults, ships, and freight cars) to control insects and rodents.
    About 70% of methyl bromide produced in the United States goes into pesticidal formulations. Nonpesticidal uses include degreasing wool and extracting oils from nuts, seeds and flowers. Methyl bromide is also a methylating agent in the chemical industry. In the past, it was used as a refrigerant and as a fire-extinguishing agent in aircraft. The chemical name for this fumigant is bromomethane.
    Methyl bromide is a Restricted Use Pesticide (RUP) because of its high acute toxicity to applicators. Restricted Use Pesticides may be purchased and used only by certified applicators.
    The bimolecular nucleophilic substitution (S(N)2) reaction of methyl bromide and OH-in aqueous solution has been investigated using a multilayered-representation quantum mechanical and molecular mechanics methodology.
  • Precautions(1) Under the law, methyl bromide may only be applied by licensed applicators or those under their direct supervision. Licensed applicators must meet strict criteria governing safe handling, storage and use of the compound, which helps to reduce exposure potential.
    (2) Workers involved in methyl bromide application or the removal of containment after fumigation are likely to have the highest risk of exposure, followed by those workers who first re-enter the area after fumigation. To reduce this risk, regulations restrict re-entry to application sites and require personal protective clothing and equipment for people who handle the product.
    (3) Because methyl bromide is absorbed by the soil and readily dissipates in the atmosphere, bystanders such as farm workers in adjacent fields and those who live or work nearby are likely less at risk. Even so, depending on soil and weather conditions and proximity to the application site, bystanders may come into contact with residues as the compound disperses.
    (4) References:
  • DescriptionMethyl bromide is a colorless liquid or gas with practically no odor. It is a poisonous gas at room temperature and atmospheric pressure. At high concentrations, it has a chloroform-like odor. Detection of lower concentrations is often facilitated by a warning odorant, chloropicrin, which is added by the manufacturer.
    Methyl bromide is flammable only in the range of 10 percent to 16 percent by volume in air. Its physical properties do not meet the definition of a flammable gas as defined by DOT and TC. The onset of thermal decomposition occurs at approximately 752°F (400°C).
  • Chemical PropertiesMethyl bromide (Bromomethane) is an odorless, sweetish, colorless gas that has been used as a soil fumigant and structural fumigant to control pests across a wide range of agricultural sectors. Methyl bromide is soluble in ethanol, benzene, carbon disulfi de, and sparingly in water. During the 1920s, methyl bromide was used as an industrial fi re extinguishing agent. The current uses of methyl bromide include the fumigation of homes and other structures for the control of termites and other pests. Because methyl bromide depletes the stratospheric ozone layer, the amount produced and imported in the United States was reduced incrementally until it was phased out on January 1, 2005, pursuant to our obligations under the Montreal Protocol on Substances that Deplete the Ozone Layer (Protocol) and the Clean Air Act (CAA).
  • Chemical PropertiesMethyl bromide is a colorless gas with a chloroform-like odor at high concentrations. A liquid below 3.3C. Shipped as a liquefied compressed gas.
  • Physical propertiesColorless liquid or gas with an odor similar to chloroform at high concentrations. Ruth (1986) reported odor threshold concentrations ranging from 80 to 4,000 mg/m3.
  • OccurrenceAn organic compound, present in the atmosphere as the result of both natural (oceanic production) and anthropogenic (use as a soil fumigant) sources; this compound is the largest single source of bromine to the stratosphere, with a tropospheric mixing ratio of about 10 parts per trillion (by volume).
  • UsesMethyl bromide is used as a pesticide, which is very effective against parasitic nematodes.
  • UsesThe primary pre-harvest uses of methyl bromide are as fumigant to control a broad spectrum of insects, nematodes, bacteria, fungi and weeds in grapes, vegetables and strawberries cultivation. Major postharvest use is in the quarantine control of agricultural commodities such as the disinfestation of potatoes and tomatoes.
  • UsesMethyl bromide is used as a fumigant forpest control, for degreasing wool, and as a methylating agent. Its use as a refrigerant andin fire extinguishers is restrained because ofits health hazards.
  • UsesSoil, space and food fumigant; disinfestation of potatoes, tomatoes and other crops.
  • UsesIn ionization chambers. For degreasing wool. Extracting oils from nuts, seeds, flowers. Soil or space fumigant for insects, fungi, rodents. Methylating agent. Has been used as fire extinguishing agent.
  • DefinitionChEBI: A one-carbon compound in which the carbon is attached by single bonds to three bromine atoms and one hydrogen atom. It is produced naturally by marine algae.
  • Production MethodsA number of reports of injury from use as a fire extinguisher can be found in the European literature.
    Methyl bromide (MeBr) is an odorless, colorless gas that has been used as a soil fumigant and structural fumigant to control pests across a wide range of agricultural sectors. Because MeBr depletes the stratospheric ozone layer, the amount of MeBr produced and imported in the United States was reduced incrementally until it was 100% phased out in January 1, 2005, pursuant to our obligations under the Montreal Protocol on Substances that Deplete the Ozone Layer (Protocol) and the Clean Air Act (CAA) with exception for allowable exemptions such as critical use exemptions agreed to by the Montreal Protocol Parties. Allowable exemptions to the phaseout include the Quarantine and Preshipment (QPS) exemption, to eliminate quarantine pests, and the critical use exemption (CUE), designed for agricultural users with no technically or economically feasible alternatives.
  • Production MethodsThe commercial manufacture of methyl bromide is based on the reaction of hydrogen bromide with methanol. The hydrogen bromide used could be generated in situ from bromine and a reducing agent. The uses of sulfur or hydrogen sulfide as reducing agents are described, the latter process having the advantage. A new continuous process for the production of methyl bromide from methanol and aqueous HBr in the presence of a silica supported heteropolyacid catalyst has recently been described. Methyl bromide can also be coproduced with other organic bromine compounds by the reaction of the methanol solvent with hydrogen bromide formed as a by-product. The processes include coproduction of methyl bromide with bromostyrenes, tribromophenol, potassium and sodium bromide, and especially tetrabromo bisphenol A.
  • ReactionsMethyl bromide is present in the atmosphere as the result of both natural (oceanic production) and anthropogenic (use as a soil fumigant) sources; this compound is the largest single source of bromine to the stratosphere, with a tropospheric mixing ratio of about 10 parts per trillion (by volume). Methyl bromide reacts with several nucleophiles and is a useful methylation agent for the preparation of ethers, sulfides, amines, etc. Tertiary amines are methylated by methyl bromide to form quaternary ammonium bromides. The reactivity of methyl bromide is summarized in Figure 1.图
  • Synthesis Reference(s)Journal of the American Chemical Society, 75, p. 1148, 1953. Applications of the Hunsdiecker Silver Salt Degradation. The Preparation of Dibromides and Tribromides. DOI: 10.1021/ja01101a041
  • General DescriptionColorless highly toxic volatile liquid or a gas. Boiling point 3.56°C (38.41°F). Usually odorless, but has a sweetish chloroform-like odor at high concentrations. Used as an insecticide, a rodenticide, a fumigant, a nematocide, a chemical intermediate and as a fire extinguishing agent.
  • Air & Water ReactionsNonflammable over a wide range of concentrations in air. Slightly soluble in water (about 1.75 g/100 mL of solution at 20° C). Reacts slowly with water to give methyl alcohol and hydrobromic acid. [K-O Vol. 4].
  • Reactivity ProfileMethyl bromide is incompatible with metals, dimethyl sulfoxide, ethylene oxide. [Lewis]. Can give flammable products if mixed with potassium hydroxide, sodium hydroxide and other strong bases. Methyl bromide in a steel tank reacted with an aluminum tube (part of the level gauge) producing methyl aluminum bromide. When the latter was subsequently exposed to air, enough heat was produced to ignite the Methyl bromide -compressed air mixture above the liquid layer. The ensuing explosion shattered the tank (also incompatible with zinc, magnesium, and alloys)[Chem. Eng. Pro. 58(8). 1962]. A reaction between Methyl bromide and dimethyl sulfoxide resulted in an explosion that shattered the apparatus [NFPA 491M. 1991].
  • HazardToxic by ingestion, inhalation, and skin absorption; strong irritant to skin and upper respiratory tract. Questionable carcinogen.
  • Health HazardExposures to methyl bromide by inhalation cause injury to the brain, nerves, lungs, and throat. At high doses, breathing methyl bromide causes injury to the kidneys and liver. The symptoms of methyl bromide toxicity and poisoning include, but are not limited to, dizziness, headache, abdominal pain, vomiting, weakness, hallucinations, loss of speech, incoordination, labored breathing, and convulsions. Contact with the skin and eyes can lead to irritation and burns. After serious exposures to methyl bromide, occupational workers suffer with lung and/or nervous system-related problems and permanent brain/ nerve damage. Laboratory study with species of animals indicated that bromomethane does not cause birth defects and does not interfere with normal reproduction except at high exposure levels
  • Health HazardMethyl bromide is a dangerous cumulative poison with delayed symptoms of central nervous system intoxication that may appear as long as several months after exposure. High concentrations can produce fatal pulmonary edema. Chronic exposure can cause central nervous system depression and kidney injury. It may cause severe and permanent brain damage. Severe neurological signs may appear when there is a sudden exposure to high concentrations following continuous slight exposure. Methyl bromide has practically no odor or irritating effects and therefore no warning, even at hazardous concentrations.
  • Fire HazardWhen heated to decomposition, Methyl bromide emits toxic fumes of bromides. Hazardous polymerization may not occur.
  • Agricultural UsesFumigant, Herbicide, Insecticide, Nematicide: The primary use of methyl bromide is as an insect fumigant to control insects, nematodes, weeds and pathogens in more than 100 crops and for soil, grain storage, warehouses, mills, ships, etc. Use of methyl bromide in the U.S. will be phased out under the requirements of the Montreal Protocol, with some exemptions. Methyl bromide is also used as a chemical intermediate and a methylating agent, a refrigerant, a herbicide, a fire-extinguishing agent, a low-boiling solvent in aniline dye manufacture, for degreasing wool, for extracting oils from nuts, seeds, and flowers, and in ionization chambers. It is used as an intermediate in the manufacture of many drugs. A U.S. EPA restricted Use Pesticide (RUP), NO INERT. Still actively registered for use in the U.S. (2013). As of March 18, 2005, the use of methyl bromide in the EU was banned for most purposes, including quarantine and pre-shipment fumigations.Registered for use in the U.S.
  • Materials UsesDry methyl bromide is inert and noncorrosive in the presence of most structural metals. However, in the presence of impurities such as alcohols and water, reactions will take place on zinc, tin, and iron surfaces. Aluminum and its alloys should not be used for methyl bromide service because of the formation of trimethyl aluminum, which is pyrophoric.
  • Safety ProfileSuspected carcinogen with experimental carcinogenic data. A human poison by inhalation. Human systemic effects by inhalation: anorexia, nausea or vomiting. Corrosive to skin; can produce severe burns. Human mutation data reported. A powerful fumigant gas that is one of the most toxic of the common organic hahdes. It is hemotoxic and narcotic with delayed action. The effects are cumulative and damaging to nervous system, hdneys, and lung. Central nervous system effects include blurred vision, mental confusion, numbness, tremors, and speech defects. Methyl bromide is reported to be eight times more toxic on inhalation than ethyl bromide. Moreover, because of its greater volatility, it is a much more frequent cause of poisoning. Death following acute poisoning is usually caused by its irritant effect on the lungs. In chronic poisoning, death is due to injury to the central nervous system. Fatal poisoning has always resulted from exposure to relatively high concentrations of methyl bromide vapors (from 8600 to 60,000 ppm). Nonfatal poisoning has resulted from exposure to concentrations as low as 100-500 ppm. In addtion to injury to the lung and central nervous system, the kidneys may be damaged, with development of albuminuria and, in fatal cases, cloudy swelhng and/or tubular degeneration. The liver may be enlarged. There are no characteristic blood changes. Mixtures of 10-1 5 percent with air may be ignited with difficulty. Moderately explosive when exposed to sparks or flame. Forms explosive mixtures with air within narrow limits at atmospheric pressure, with wider limits at higher pressure. The explosive sensitivity of mixtures with air may be increased by the presence of aluminum, magnesium, zinc, or their alloys. Incompatible with metals, dunethyl sulfoxide, ethylene oxide. To fight fire, use foam, water, CO2, dry chemical. When heated to decomposition it emits toxic fumes of Br-. See also BROMIDES
  • Potential ExposureMethyl bromide is used in fire extinguishers; as a fumigant in pest control and as a methylation agent in industry as an insect fumigant for soil, grain, warehouses, mills, ships, etc. It is also used as a chemical intermediate and a methylating agent; a refrigerant; a herbicide; a low-boiling solvent in aniline dye manufacture; for degreasing wool; for extracting oils from nuts, seeds, and flowers; and in ionization chambers. It is used as an intermediate in the manufacture of many drugs.
  • Physiological effectsMethyl bromide is toxic. The vapor is odorless at low concentrations and nonirritating to the skin or eyes during exposure; therefore, detection of overexposure is not possible until the onset of symptoms. Early symptoms of overexposure are dizziness, headache, nausea and vomiting, weakness, and collapse. Lung edema may develop 2 to 48 hours after exposure, accompanied by cardiac irregularities. These effects may cause death. Repeated overexposures can result in blurred vision, staggering gait, and mental imbalance, with probable recovery after a period of no exposure. Blood bromide levels suggest the occurrence, but not the degree, of exposure. Treatment is symptomatic.
    ACGIH recommends the Threshold Limit Value-Time-Weighted Average (TLV- TWA) of I ppm (3.9 mg/m3 ) for methyl bromide. The TLV- TWA is the time-weighted average concentration for a normal 8-hour workday and a 40-hour workweek, to which nearly all workers may be repeatedly exposed, day after day, without adverse effect.
  • CarcinogenicityData on the carcinogenicity of bromomethane for oral exposure are lacking, but oral exposure is unlikely due to the volatility of bromomethane. A 1-year study in dogs consuming bromomethane-exposed food found no evidence of carcinogenicity. Data on carcinogenicity in humans following inhalation exposure in humans are not available. Animal inhalation studies exist but do not demonstrate evidence of bromomethane-induced carcinogenic changes. They include studies in F344 and Wistar rats, and in B6C3F1 and Crj:BDF1. The EPA descriptor for cancer is “inadequate information to assess the carcinogenic potential of bromomethane in humans.” Specifically, IRIS states: “Inadequate human and animal data: a single mortality study from which direct exposure associations could not be deduced and studies in several animal species with too few animals, too brief exposure or observation time for adequate power.” Bromomethane has shown genotoxicity. NAS reported that although methyl bromide is genotoxic without metabolic activation and has been shown to alkylate DNA in different organs in in vivo studies, there is no clear evidence of oncogenicity under experimental conditions used in the chronic inhalation studies with rat and mice.
  • SourceDrinking water standard: No MCLGs or MCLs have been proposed, however, a DWEL of 50 μg/L was recommended (U.S. EPA, 2000).
  • Environmental FatePhotolytic. When methyl bromide and bromine gas (concentration = 3%) was irradiated at 1850 ?, methane was produced (Kobrinsky and Martin, 1968).
    Chemical/Physical. Methyl bromide hydrolyzes in water forming methanol and hydrobromic acid. The estimated hydrolysis half-life in water at 25°C and pH 7 is 20 days (Mabey and Mill, 1978). Forms a voluminous crystalline hydrate at 0–5°C (Keith and Walters, 1992).
    When methyl bromide was heated to 550°C in the absence of oxygen, methane, hydrogen, bromine, ethyl bromide, anthracene, pyrene and free radicals were produced (Chaigneau et al., 1966).
    Emits toxic bromide fumes when heated to decomposition (Lewis, 1990).
  • Metabolic pathwayMethyl bromide degrades in aqueous and soil environments mainly via dehalogenation to yield bromide ions with the incorporation of the methyl carbon moiety into polar natural components.
  • storageMethyl bromide (Bromomethane) should be kept stored in sealed containers to keep it from evaporating.
  • ShippingUN1062 Methyl bromide, Hazard Class: 2.3; Labels: 2.3-Poisonous gas, Inhalation Hazard Zone C. Cylinders must be transported in a secure upright position, in a well-ventilated truck. Protect cylinder and labels from physical damage. The owner of the compressed gas cylinder is the only entity allowed by federal law (49CFR) to transport and refill them. It is a violation of transportation regulations to refill compressed gas cylinders without the express written permission of the owner
  • Purification MethodsPurify it by bubbling through conc H2SO4, followed by passage through a tube containing glass beads coated with P2O5. Also purify it by distillation from AlBr3 at -80o, by passage through a tower of KOH pellets and by partial condensation. [Beilstein 1 IV 68.]
  • DegradationMethyl bromide is hydrolysed at neutral pH to methanol and bromide ion. The DT50s of methyl bromide in water at 17 and 25 °C were 21 and 75 days, respectively (Jeffers and Wolfe, 1996a; Mabey and Mill, 1978; Moelwyn-Hughes, 1938). Aqueous photolysis is not a major environmental degradation process.
    In the upper and mid stratosphere (>20 km), photodegradation of MeBr with hydroxy radicals is reported to yield various products such as Br, BrO and HBr (Honaganahalli and Seiber, 1996).
  • IncompatibilitiesAttacks aluminum to form spontaneously flammable aluminum trimethyl. Incompatible with strong oxidizers, aluminum, dimethylsulfoxide, ethylene oxide; water. Attacks zinc, magnesium, alkali metals and their alloys. Attacks some rubbers and coatings. Methyl bromide reacts with water to generate hydrobromic acid and methanol but the reaction is so slow that it can be disregarded for most practical purposes.
  • Waste DisposalConsult with environmental regulatory agencies for guidance on acceptable disposal practices. Generators of waste containing this contaminant (≥100 kg/mo) must conform to EPA regulations governing storage, transportation, treatment, and waste disposal. A poisonous gas. Must be handled by experts: the recommended disposal procedure is to spray the gas into the fire box of an incinerator equipped with an afterburner and scrubber (alkali).
  • PrecautionsOccupational workers should use appropriate ventilation during production and formulation of bromomethane at the workplace. The ventilation must be suffi cient to maintain the levels of bromomethane below the prescribed OEL. Local exhaust ventilation at source or vapor extraction may also be used. Gloves or rubber boots should not be used as the liquid or concentrated vapor may be trapped inside them
  • GRADES AVAILABLEMethyl bromide is sold either as a pure compound, 99.8 percent minimum, or with an odorant, chloropicrin (typically 2 percent).
Methyl bromide Preparation Products And Raw materials
Methyl bromide (74-83-9)Related Product Information
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