Bromomethane

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Bromomethane
Natta projection of bromomethane.svg
Ball and stick model of bromomethane Bromomethane-3D-balls.png
Ball and stick model of bromomethane
Spacefill model of bromomethane Bromomethane-3D-vdW.png
Spacefill model of bromomethane
Names
Preferred IUPAC name
Bromomethane [1]
Identifiers
3D model (JSmol)
1209223
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.000.740 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 200-813-2
916
KEGG
MeSH methyl+bromide
PubChem CID
RTECS number
  • PA4900000
UNII
UN number 1062
  • InChI=1S/CH3Br/c1-2/h1H3 Yes check.svgY
    Key: GZUXJHMPEANEGY-UHFFFAOYSA-N Yes check.svgY
  • CBr
Properties
CH3Br
Molar mass 94.939 g·mol−1
AppearanceColorless gas [2]
Odor Chloroform-like
Density 3.97 kg/m3 (gas, 0 °C) [2]
1.72 g/mL (liquid, 4 °C) [2]
Melting point −93.66 °C (−136.59 °F; 179.49 K) [2]
Boiling point 4.0 °C (39.2 °F; 277.1 K) [2]
17.5 gL−1 [2]
log P 1.3
Vapor pressure 190 kPa (at 20 °C, 68 °F)
−42.8·10−6 cm3·mol−1
Thermochemistry
−35.1  −33.5 kJ·mol−1
Hazards
GHS labelling:
GHS-pictogram-skull.svg GHS-pictogram-exclam.svg GHS-pictogram-silhouette.svg GHS-pictogram-pollu.svg
Danger
H301, H315, H319, H331, H335, H341, H373, H400, H420
P201, P202, P260, P261, P264, P270, P271, P273, P280, P281, P301+P310, P302+P352, P304+P340, P305+P351+P338, P308+P313, P311, P312, P314, P321, P330, P332+P313, P337+P313, P362, P391, P403+P233, P405, P501, P502
NFPA 704 (fire diamond)
NFPA 704.svgHealth 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasFlammability 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g. canola oilInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
3
1
0
Flash point 194 °C (381 °F; 467 K) [2]
535 °C (995 °F; 808 K) [2]
Explosive limits 10-16% [3]
Lethal dose or concentration (LD, LC):
  • 1200 ppm (mouse, 1 hr)
  • 7316 ppm (rabbit, 30 min)
  • 2833 ppm (rat, 1 hr)
  • 302 ppm (rat, 8 hr)
  • 390 ppm (mouse, 9 hr) [4]
300 ppm (guinea pig, 9 hr) [4]
NIOSH (US health exposure limits):
PEL (Permissible)
C 20 ppm (80 mg/m3) [skin] [3]
REL (Recommended)
Ca [3]
IDLH (Immediate danger)
Ca [250 ppm] [3]
Related compounds
Related alkanes
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Yes check.svgY  verify  (what is  Yes check.svgYX mark.svgN ?)

Bromomethane, commonly known as methyl bromide, is an organobromine compound with formula C H 3 Br. This colorless, odorless, nonflammable gas is produced both industrially and biologically. It has a tetrahedral shape and it is a recognized ozone-depleting chemical. It was used extensively as a pesticide until being phased out by most countries in the early 2000s. [5]

Contents

Occurrence and manufacture

Bromomethane originates from both natural and human sources. In the ocean, marine organisms are estimated to produce 56,000 tonnes annually. [6] It is also produced in small quantities by certain terrestrial plants, such as members of the family Brassicaceae. It is manufactured for agricultural and industrial use by treating methanol with bromine in the presence of sulfur or hydrogen sulfide: [5]

6 CH3OH + 3 Br2 + S → 6 CH3Br + 2 H2O + H2SO4

An intermediate in this process is sulfur hexabromide. [7]

Uses

In 1999, an estimated 71,500 tonnes of synthetic methyl bromide were used annually worldwide. [8] 97% of this estimate was used for fumigation purposes, whilst 3% was used for the manufacture of other products. Moreover, 75% of the consumption used to take place in developed nations, led by the United States (43%) and Europe (24%). Asia and the Middle East combined to use 24% whereas Latin America and Africa had the lowest usage at 9%. [8]

ISPM 15 markings on a pallet from China. The MB indicates the wood has been fumigated with methyl bromide to kill pests. China methyl bromide pallet.jpg
ISPM 15 markings on a pallet from China. The MB indicates the wood has been fumigated with methyl bromide to kill pests.

Until its production and use was curtailed by the Montreal Protocol, bromomethane was widely applied as a soil sterilant, mainly for production of seed but also for some crops such as strawberries [9] and almonds. In commercial large-scale monoculture seed production, unlike crop production, it is of vital importance to avoid contaminating the crop with off-type seed of the same species. Therefore, selective herbicides cannot be used. Although bromomethane is dangerous, it is considerably safer and more effective than some other soil sterilants. Its loss to the seed industry has resulted in changes to cultural practices, with increased reliance on soil steam sterilization, mechanical roguing, and fallow seasons. Bromomethane was also used as a general-purpose fumigant to kill a variety of pests including rats and insects. Bromomethane has poor fungicidal properties. Bromomethane is the only fumigant allowed (heat treatment is the only other option) under ISPM 15 regulations when exporting solid wood packaging (fork lift pallets, crates, bracing) to ISPM 15 compliant countries. Bromomethane is used to prepare golf courses, particularly to control Bermuda grass. The Montreal Protocol stipulates that bromomethane use be phased out.

Bromomethane is also a precursor in the manufacture of other chemicals as a methylating agent. [5]

Bromomethane was once used in specialty fire extinguishers, prior to the advent of less toxic halons, as it is electrically non-conductive and leaves no residue. It was used primarily for electrical substations, military aircraft, and other industrial hazards. It was never as popular as other agents due to its high cost and toxicity. Bromomethane was used from the 1920s to the 1960s, and continued to be used in aircraft engine fire suppression systems into the late 1960s.

A selection of stored-pressure bromomethane fire extinguishers, circa 1930s-40s, UK National Methyl Bromide extinguisher.jpg
A selection of stored-pressure bromomethane fire extinguishers, circa 1930s-40s, UK

Regulation

Bromomethane is readily photolyzed in the atmosphere to release bromine radicals, which are far more destructive to stratospheric ozone than chlorine. As such, it is subject to phase-out requirements of the 1987 Montreal Protocol on Ozone Depleting Substances.

The London Amendment in 1990 added bromomethane to the list of ODS to be phased out. Phase-out began in the United States in 1993, manufactured amounts being capped at the 1991 level. All developed countries in the Montreal Protocol reduced both manufactured and imported amounts by 25% in 1999, 50% 2001, 75% 2003, 100% 2005. [10] In 2003 the Global Environment Facility approved funds for a UNEP-UNDP joint project for methyl bromide total sector phase out in seven countries in Central Europe and Central Asia, which was due for completion in 2007. [11]

Australia

In Australia, bromomethane is the preferred fumigant of the Department of Agriculture and Water Resources for most organic goods imported into Australia. [12] The department conducts methyl bromide fumigation certification for both domestic and foreign fumigators who can then fumigate containers destined for Australia. A list of alternative fumigants is available for goods imported from Europe (in what's known as the BICON database), where methyl bromide fumigation has been banned. [13] Alternatively, the department allows containers from Europe to be fumigated with methyl bromide on arrival to Australia.

New Zealand

In New Zealand, bromomethane is used as a fumigant for whole logs destined for export. Environmental groups and the Green Party oppose its use. [14] [15] In May 2011 the Environmental Risk Management Authority (ERMA) introduced new rules for its use which restrict the level of public exposure to the fumigant, set minimum buffer zones around fumigation sites, provide for notification to nearby residents and require users to monitor air quality during fumigations and report back to ERMA each year. All methyl bromide fumigations must use recapture technology by 2025. [16]

United States

In the United States bromomethane is regulated as a pesticide under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA; 7 U.S.C. 136 et seq.) and as a hazardous substance under the Resource Conservation and Recovery Act (RCRA; 42 U.S.C. 6901 et seq.), and is subject to reporting requirements under the Emergency Planning and Community Right-to-Know Act (EPCRA; 42 U.S.C. 11001 et seq.). The U.S. Clean Air Act (CAA; 42 U.S.C. 7401 et seq.). A 1998 amendment (P.L. 105-178, Title VI) conformed the Clean Air Act phase out date with that of the Montreal Protocol. [17] [18] [10] Whereas the Montreal Protocol has severely restricted the use of bromomethane internationally, the United States has successfully lobbied for critical-use exemptions. [19] Critical use exemptions allow the United States to continue using MeBr until it is scheduled to be completely phased out sometime in 2017. [20] Bromomethane was still in use in the United States for cherries exported to South Korea as of 2022.[ citation needed ]

In 2004, over 7 million pounds (3,200 t) of bromomethane were applied in California. Applications include tomato, strawberry, and ornamental shrub growers, and fumigation of ham/pork products. Also exempt is the treatment of solid wood packaging (forklift pallets, crates, bracing), and the packaged goods, being exported to ISPM 15 countries (to include Canada in 2012).[ citation needed ]

Chile

Chile has phased out the use of bromomethane in traditional agriculture as of 2015, with exemption of the 100% pure formulation that is largely used for quarantine pest control and at pre-shipments of the fruit export industry. [21]

Alternatives

Alternatives to bromomethane in the agricultural field are currently in use and further alternatives are in development, including propylene oxide and furfural. [22] For Australia a list of alternative fumigants is available for goods imported from Europe (in what's known as the BICON database), where methyl bromide fumigation has been banned. [13]

Potential future alternatives

Health effects

Brief exposure to high concentrations and prolonged inhalation of lower concentrations are problematic. [23] Exposure levels leading to death vary from 1,600 to 60,000 ppm, depending on the duration of exposure (as a comparison exposure levels of 70 to 400 ppm of carbon monoxide cover the same spectrum of illness/death). Concentrations in the range of 60,000 ppm can be immediately fatal, while toxic effects can present following prolonged exposure to concentrations well under 1,000 ppm.

"A TLV–TWA of 1 ppm (3.89 mg/m3) is recommended for occupational exposure to methyl bromide"-ACGIH 8 hour time weighted average. Immediately Dangerous To Life or Health Concentration by NIOSH: "The revised IDLH for methyl bromide is 250 ppm based on acute inhalation toxicity data in humans [Clarke et al. 1945]. This may be a conservative value due to the lack of relevant acute toxicity data for workers exposed to concentrations above 220 ppm. [Note: NIOSH recommends as part of its carcinogen policy that the "most protective" respirators be worn for methyl bromide at any detectable concentration.]" Detectable concentration by Drager Tube is 0.5 ppm.

Respiratory, kidney, and neurological effects are of the greatest concern.

Treatment of wood packaging requires a concentration of up to 16,000 ppm.

NIOSH considers methyl bromide to be a potential occupational carcinogen as defined by the OSHA carcinogen policy [29 CFR 1990]. "Methyl bromide showed a significant dose-response relationship with prostate cancer risk." [24]

Excessive exposure

Expression of toxicity following exposure may involve a latent period of several hours, followed by signs such as nausea, abdominal pain, weakness, confusion, pulmonary edema, and seizures. Individuals who survive the acute phase often require a prolonged convalescence. Persistent neurological deficits such as asthenia, cognitive impairment, optical atrophy, and paresthesia are frequently present after moderate to severe poisoning. Blood or urine concentrations of inorganic bromide, a bromomethane metabolite, are useful to confirm a diagnosis of poisoning in hospitalized patients or to assist in the forensic investigation of a case of fatal overdosage. [25]

See also

Related Research Articles

<span class="mw-page-title-main">Bromine</span> Chemical element, symbol Br and atomic number 35

Bromine is a chemical element; it has symbol Br and atomic number 35. It is a volatile red-brown liquid at room temperature that evaporates readily to form a similarly coloured vapour. Its properties are intermediate between those of chlorine and iodine. Isolated independently by two chemists, Carl Jacob Löwig and Antoine Jérôme Balard, its name was derived from the Ancient Greek βρῶμος (bromos) meaning "stench", referring to its sharp and pungent smell.

<span class="mw-page-title-main">Phosgene</span> Toxic gaseous compound (COCl2)

Phosgene is an organic chemical compound with the formula COCl2. It is a toxic, colorless gas; in low concentrations, its musty odor resembles that of freshly cut hay or grass. It can be thought of chemically as the double acyl chloride analog of carbonic acid, or structurally as formaldehyde with the hydrogen atoms replaced by chlorine atoms. Phosgene is a valued and important industrial building block, especially for the production of precursors of polyurethanes and polycarbonate plastics.

<span class="mw-page-title-main">1,2-Dibromoethane</span> Chemical compound

1,2-Dibromoethane, also known as ethylene dibromide (EDB), is an organobromine compound with the chemical formula C
2
H
4
Br
2
. Although trace amounts occur naturally in the ocean, where it is probably formed by algae and kelp, it is mainly synthetic. It is a dense colorless liquid with a faint, sweet odor, detectable at 10 ppm, and is a widely used and sometimes-controversial fumigant. The combustion of 1,2-dibromoethane produces hydrogen bromide gas that is significantly corrosive.

<span class="mw-page-title-main">Phosphine</span> Chemical compound hydrogen phosphide

Phosphine (IUPAC name: phosphane) is a colorless, flammable, highly toxic compound with the chemical formula PH3, classed as a pnictogen hydride. Pure phosphine is odorless, but technical grade samples have a highly unpleasant odor like rotting fish, due to the presence of substituted phosphine and diphosphane (P2H4). With traces of P2H4 present, PH3 is spontaneously flammable in air (pyrophoric), burning with a luminous flame. Phosphine is a highly toxic respiratory poison, and is immediately dangerous to life or health at 50 ppm. Phosphine has a trigonal pyramidal structure.

<span class="mw-page-title-main">Dichloromethane</span> Chemical compound

Dichloromethane is an organochlorine compound with the formula CH2Cl2. This colorless, volatile liquid with a chloroform-like, sweet odor is widely used as a solvent. Although it is not miscible with water, it is slightly polar, and miscible with many organic solvents.

Chloromethane, also called methyl chloride, Refrigerant-40, R-40 or HCC 40, is an organic compound with the chemical formula CH3Cl. One of the haloalkanes, it is a colorless, sweet-smelling, flammable gas. Methyl chloride is a crucial reagent in industrial chemistry, although it is rarely present in consumer products, and was formerly utilized as a refrigerant. Most chloromethane is biogenic.

<span class="mw-page-title-main">1,1,1-Trichloroethane</span> Solvent, now banned for ozone depletion

The organic compound 1,1,1-trichloroethane, also known as methyl chloroform and chlorothene, is a chloroalkane with the chemical formula CH3CCl3. It is an isomer of 1,1,2-trichloroethane. This colorless, sweet-smelling liquid was once produced industrially in large quantities for use as a solvent. It is regulated by the Montreal Protocol as an ozone-depleting substance and its use is being rapidly phased out.

<span class="mw-page-title-main">Fumigation</span> Pest control technique

Fumigation is a method of pest control or the removal of harmful microorganisms by completely filling an area with gaseous pesticides, or fumigants, to suffocate or poison the pests within. It is used to control pests in buildings, soil, grain, and produce. Fumigation is also used during the processing of goods for import or export to prevent the transfer of exotic organisms.

<span class="mw-page-title-main">Sulfuryl fluoride</span> Chemical compound

Sulfuryl fluoride (also spelled sulphuryl fluoride) is an inorganic compound with the formula SO2F2. It is an easily condensed gas and has properties more similar to sulfur hexafluoride than sulfuryl chloride, being resistant to hydrolysis even up to 150 °C. It is neurotoxic and a potent greenhouse gas, but is widely used as a fumigant insecticide to control termites.

Chloropicrin, also known as PS and nitrochloroform, is a chemical compound currently used as a broad-spectrum antimicrobial, fungicide, herbicide, insecticide, and nematicide. It was used as a poison gas in World War I. Its chemical structural formula is Cl3C−NO2.

<span class="mw-page-title-main">Ethyl formate</span> Chemical compound

Ethyl formate is an ester formed when ethanol reacts with formic acid. Ethyl formate has the characteristic smell of rum and is partially responsible for the flavor of raspberries, occurring naturally in some plant oils, fruits, and juices. Ethyl formate does not occur naturally in the animal kingdom.

<span class="mw-page-title-main">Hydrogen selenide</span> Chemical compound

Hydrogen selenide is an inorganic compound with the formula H2Se. This hydrogen chalcogenide is the simplest and most commonly encountered hydride of selenium. H2Se is a colorless, flammable gas under standard conditions. It is the most toxic selenium compound with an exposure limit of 0.05 ppm over an 8-hour period. Even at extremely low concentrations, this compound has a very irritating smell resembling that of decayed horseradish or "leaking gas", but smells of rotten eggs at higher concentrations.

Iodomethane, also called methyl iodide, and commonly abbreviated "MeI", is the chemical compound with the formula CH3I. It is a dense, colorless, volatile liquid. In terms of chemical structure, it is related to methane by replacement of one hydrogen atom by an atom of iodine. It is naturally emitted by rice plantations in small amounts. It is also produced in vast quantities estimated to be greater than 214,000 tons annually by algae and kelp in the world's temperate oceans, and in lesser amounts on land by terrestrial fungi and bacteria. It is used in organic synthesis as a source of methyl groups.

<span class="mw-page-title-main">1,3-Dichloropropene</span> Chemical compound

1,3-Dichloropropene, sold under diverse trade names, is an organochlorine compound with the formula C3H4Cl2. It is a colorless liquid with a sweet smell. It is feebly soluble in water and evaporates easily. It is used mainly in farming as a pesticide, specifically as a preplant fumigant and nematicide. It is widely used in the US and other countries, but is banned in 34 countries.

<span class="mw-page-title-main">Bromochloromethane</span> Chemical compound

Bromochloromethane or methylene bromochloride and Halon 1011 is a mixed halomethane. It is a heavy low-viscosity liquid with refractive index 1.4808.

<span class="mw-page-title-main">Dichlorofluoromethane</span> Chemical compound

Dichlorofluoromethane or Freon 21 or R 21 is a halomethane or hydrochlorofluorocarbon with the formula CHCl2F. It is a colorless and odorless gas. It is produced by fluorination of chloroform using a catalyst such as antimony trifluoride:

<span class="mw-page-title-main">1-Bromopropane</span> Chemical compound

1-Bromopropane (n-propylbromide or nPB) is an organobromine compound with the chemical formula CH3CH2CH2Br. It is a colorless liquid that is used as a solvent. It has a characteristic hydrocarbon odor. Its industrial applications increased dramatically in the 21st century due to the phasing out of chloro­fluoro­carbons and chloro­alkanes such as 1,1,1-Trichloro­ethane under the Montreal Protocol.

Organobromine chemistry is the study of the synthesis and properties of organobromine compounds, also called organobromides, which are organic compounds that contain carbon bonded to bromine. The most pervasive is the naturally produced bromomethane.

<span class="mw-page-title-main">Ethylene thiourea</span> Chemical compound

Ethylene thiourea (ETU) is an organosulfur compound with the formula C3H6N2S. It is an example of an N,N-disubstituted thiourea. It is a white solid. It is synthesized by treating ethylenediamine with carbon disulfide.

<span class="mw-page-title-main">Sulfotep</span> Chemical compound

Sulfotep (also known as tetraethyldithiopyrophosphate and TEDP) is a pesticide commonly used in greenhouses as a fumigant. The substance is also known as Dithione, Dithiophos, and many other names. Sulfotep has the molecular formula C8H20O5P2S2 and belongs to the organophosphate class of chemicals. It has a cholinergic effect, involving depression of the cholinesterase activity of the peripheral and central nervous system of insects. The transduction of signals is disturbed at the synapses that make use of acetylcholine. Sulfotep is a mobile oil that is pale yellow-colored and smells like garlic. It is primarily used as an insecticide.

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