Bromochloromethane

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Bromochloromethane

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Template:Longitem	1730801
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EC Number	Template:Unbulleted list
Template:Longitem	25577
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MeSH	bromochloromethane
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UN number	1887
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Molar mass	Template:Chem molar mass
Appearance	Colorless liquid
Odor	Chloroform-like
Density	1.991g·mL−1
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log P	1.55
Vapor pressure	15.60kPa (at 20.0°C)
Template:Longitem	−86.88·10−6·cm3/mol
Template:Longitem	1.482
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Template:Longitem	2-Chloroethanol

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

Halon 1011 was invented for use in fire extinguishers in Germany during the mid-1940s, in an attempt to create a less toxic, more effective alternative to carbon tetrachloride. This was a concern in aircraft and tanks as carbon tetrachloride produced highly toxic by-products when discharged onto a fire. It was slightly less toxic, and used up until the late 1960s, being officially banned by the NFPA for use in fire extinguishers in 1969, as safer and more effective agents such as halon 1211 and 1301 were developed. Due to its ozone depletion potential its production was banned from January 1, 2002, at the Eleventh Meeting of the Parties for the Montreal Protocol on Substances that Deplete the Ozone Layer.

File:Aircraft A-20 CBM.jpg

A 1950s US CBM fire extinguisher.

File:Pyrene 1qt. pump-type chlorobromomethane.jpg

Pyrene 1qt. pump-type chlorobromomethane (CB or CBM), 1960s, UK

Bromochloromethane's biodegradation is catalyzed by the hydrolase enzyme alkylhalidase:

CH₂BrCl + H₂O → CH₂O + HBr + HCl

Preparation

Bromochloromethane is prepared commercially from dichloromethane:

6 CH₂Cl₂ + 3 Br₂ + 2 Al → 6 CH₂BrCl + 2 AlCl₃

CH₂Cl₂ + HBr → CH₂BrCl + HCl

The latter route requires aluminium trichloride as a catalyst. The bromochloromethane is often used as a precursor to methylene bromide.

External links

• International Chemical Safety Card 0392
• Notice with Respect to n-Propyl Bromide and Bromochloromethane
• Chemical fact sheet
• Data sheet at albemarle.com