Halon_1011

Bromochloromethane

Bromochloromethane

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.

Quick Facts Names, Identifiers ...

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.

A 1950s US CBM fire extinguisher.
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.[3]

References

  1. [1]
    NIOSH Pocket Guide to Chemical Hazards. "#0123". National Institute for Occupational Safety and Health (NIOSH).
  2. [2]
    "Chlorobromomethane". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
  3. [3]
    Dagani, M. J.; Barda, H. J.; Benya, T. J.; Sanders, D. C. "Bromine Compounds". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a04_405. ISBN 978-3527306732.
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