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Methyl bromide

Bromomethane
Stereo, skeletal formula of bromomethane with all explicit hydrogens added
Ball and stick model of bromomethane
Spacefill model of bromomethane
Names
IUPAC name
Bromomethane
Identifiers
74-83-9 YesY
3D model (Jmol) Interactive image
1209223
ChEBI CHEBI:39275 YesY
ChEMBL ChEMBL48339 YesY
ChemSpider 6083 YesY
ECHA InfoCard 100.000.740
EC Number 200-813-2
916
KEGG C18447 YesY
MeSH methyl+bromide
PubChem 6323
RTECS number PA4900000
Properties
CH3Br
Molar mass 94.94 g·mol−1
Appearance Colorless gas
Odor Chloroform-like
Density 3.97 kg/m3 (gas, 0 °C)
1.72 g/mL (liquid, 4 °C)
Melting point −93.66 °C (−136.59 °F; 179.49 K)
Boiling point 4.0 °C (39.2 °F; 277.1 K)
17.5 g L−1
log P 1.3
Vapor pressure 190 kPa (at 20 °C (68 °F))
-42.8·10−6 cm3/mol
Thermochemistry
−35.1–−33.5 kJ mol−1
Hazards
Toxic T Dangerous for the Environment (Nature) N
R-phrases R23/25, R36/37/38, R48/20, R50, R59, R68
S-phrases (S1/2), S15, S27, S36/39, S38, S45, S59, S61
NFPA 704
Flammability code 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g., canola oil Health code 3: Short exposure could cause serious temporary or residual injury. E.g., chlorine gas Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazards (white): no codeNFPA 704 four-colored diamond
Flash point 194 °C (381 °F; 467 K)
535 °C (995 °F; 808 K)
Explosive limits 10%-16%
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)
300 ppm (guinea pig, 9 hr)
US health exposure limits (NIOSH):
PEL (Permissible)
C 20 ppm (80 mg/m3) [skin]
REL (Recommended)
Ca
IDLH (Immediate danger)
Ca [250 ppm]
Related compounds
Related alkanes
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
YesY  (what is YesYN ?)
Infobox references

Bromomethane, commonly known as methyl bromide, is an organobromine compound with formula CH3Br. This colorless, odorless, nonflammable gas is produced both industrially and particularly 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.

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

In 1999, an estimated 71,500 tonnes of synthetic methyl bromide were used annually worldwide. 97% of this estimate is used for fumigation purposes, whilst 3% is used for the manufacture of other products. Moreover, 75% of the consumption takes place in developed nations, led by the U.S. (43%) and Europe (24%). Asia and the Middle East combine to use 24% whereas Latin America and Africa have the lowest consumption rates at 9%.

Until its production and use was curtailed by the , bromomethane was widely applied as a soil sterilant, mainly for production of seed but also for some crops such as strawberries 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. Whereas 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 rogueing, 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 only other option) under ISPM 15 regulations when exporting solid wood packaging (forklift 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.


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