Methyl bromide
- CAS No.
- 74-83-9
- Chemical Name:
- Methyl bromide
- Synonyms
- BROMOMETHANE;CH3Br;Mebr;Edco;Methane, bromo-;(mono)bromomethane;Dowfume mc-2 soil fumigant;METHYLBROMID AMPULLE 20 G;Celfume;Halon 1001
- CBNumber:
- CB9197705
- Molecular Formula:
- CH3Br
- Molecular Weight:
- 94.94
- MOL File:
- 74-83-9.mol
- Modify Date:
- 2024/3/14 15:18:30
| Melting point | −94 °C(lit.) |
|---|---|
| Boiling point | 4 °C(lit.) |
| Density | 1.7 g/cm3 |
| 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 Constant | 0.72 at 21 °C (Gan and Yates, 1996) |
| Exposure limits | NIOSH REL: IDLH 250 ppm; OSHA PEL: C 20 ppm; ACGIH TLV: TWA 5 ppm. |
| Dielectric constant | 9.8（0℃） |
| Stability | Stable. Incompatible with oxidizing agents, strong acids. This is an ozone-depleting chemical, and its use is restricted in many countries. |
| LogP | 1.190 |
| CAS DataBase Reference | 74-83-9(CAS DataBase Reference) |
| IARC | 3 (Vol. 41, Sup 7, 71) 1999 |
| NIST Chemistry Reference | Methyl bromide(74-83-9) |
| EPA Substance Registry System | Methyl bromide (74-83-9) |
SAFETY
Risk and Safety Statements
| Symbol(GHS) |      GHS06,GHS08,GHS09,GHS02,GHS07 |
|||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Signal word | Danger | |||||||||
| Hazard statements | H225-H301+H311+H331-H370-H302+H332-H315-H319-H335-H336-H341-H373-H400-H420-H280-H301+H331 | |||||||||
| Precautionary statements | P210-P280-P302+P352+P312-P304+P340+P312-P370+P378-P403+P235-P261-P273-P281-P305+P351+P338-P301+P310-P311 | |||||||||
| Hazard Codes | T,N,Xn,F,F+ | |||||||||
| Risk Statements | 23/25-36/37/38-48/20-50-59-68-38-20/22-11-67-66-19-12-39/23/24/25-23/24/25 | |||||||||
| Safety Statements | 15-27-36/39-38-45-59-61-36/37-26-24-16-7 | |||||||||
| RIDADR | UN 1062 2.3 | |||||||||
| WGK Germany | 3 | |||||||||
| RTECS | PA4900000 | |||||||||
| DOT Classification | 2.3, Hazard Zone C (Gas poisonous by inhalation) | |||||||||
| HazardClass | 2.3 | |||||||||
| HS Code | 29033990 | |||||||||
| Toxicity | LC for rats in air (6 hrs): 514 ppm (Irish) | |||||||||
| IDLA | 250 ppm | |||||||||
| NFPA 704 |
|
Methyl bromide Chemical Properties,Uses,Production
Description
Methyl 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 Properties
Methyl 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 properties
Colorless 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.
Occurrence
An 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).
Uses
Methyl 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.
Definition
ChEBI: 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 Methods
The 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.
Reactions
Methyl 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.
General Description
Colorless 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 Reactions
Nonflammable 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 Profile
Methyl 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].
Hazard
Toxic by ingestion, inhalation, and skin absorption; strong irritant to skin and upper respiratory tract. Questionable carcinogen.
Health Hazard
Methyl 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 Hazard
When heated to decomposition, Methyl bromide emits toxic fumes of bromides. Hazardous polymerization may not occur.
Agricultural Uses
Fumigant, 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.
Trade name
BROM-O-GAS®; BROM-OSOL ®; DAWSON® 100; DOWFUME®; EDCO®; EMBAFUME®; HALON 1001®; ISCOBROME®; KAYAFUME®; MATABROM®; METHO-GAS®; M-B-C FUMIGANT®; R 40B1®; ROTOX®; TERABOL®; TERR-O-GAS®; ZYTOX®
Materials Uses
Dry 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.
Potential Exposure
Methyl 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.
Carcinogenicity
Data 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.
Environmental Fate
Photolytic. 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 pathway
Methyl 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.
storage
Methyl bromide (Bromomethane) should be kept stored in sealed containers to keep it from evaporating.
Shipping
UN1062 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 Methods
Purify 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.]
Incompatibilities
Attacks 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 Disposal
Consult 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).
Precautions
Occupational 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
Methyl bromide Preparation Products And Raw materials
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