Bromochloromethane

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

Bromochloromethane
Names
Preferred IUPAC name
Bromo(chloro)methane
Other names
  • Bromochloromethane
  • Borothene
  • Chloromethyl bromide
  • Halon 1011[1]
  • Methylene bromochloride
  • Methyl chlorobromide[1]
  • Monochloromonobromomethane
  • Chlorobromomethane[1]
  • Fluorocarbon 1011[1]
Identifiers
3D model (JSmol)
3DMet
Abbreviations
  • BCM
  • CBM[1]
  • UN 1887
1730801
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.000.752
EC Number
  • 200-826-3
25577
KEGG
MeSH bromochloromethane
RTECS number
  • PA5250000
UNII
UN number 1887
Properties
CH2BrCl
Molar mass 129.38 g·mol−1
Appearance Colorless liquid
Odor Chloroform-like[1]
Density 1.991 g·mL−1
Melting point −88.0 °C; −126.3 °F; 185.2 K
Boiling point 68 °C; 154 °F; 341 K
16.7 g·L−1
log P 1.55
Vapor pressure 15.60 kPa (at 20.0 °C)
−86.88·10−6·cm3/mol
1.482
Hazards
GHS pictograms
GHS Signal word Danger
H315, H318, H332, H335
P261, P280, P305+351+338
Flash point Non-combustible [1]
Lethal dose or concentration (LD, LC):
  • 5 g·mol−1 (oral, rat)
  • 20 g·kg−1 (dermal, rabbit)
  • 4300 mg·kg−1 (oral, mouse)[2]
3000 ppm (mouse, 7 hr)[2]
  • 28,800 ppm (rat, 15 min)
  • 29,000 ppm (rat, 15 min)
  • 27,000 ppm (mouse, 15 min)[2]
NIOSH (US health exposure limits):
PEL (Permissible)
 TWA 200 ppm (1050 mg/m3)[1]
REL (Recommended)
 TWA 200 ppm (1050 mg/m3)[1]
IDLH (Immediate danger)
 2000 ppm[1]
Related compounds
Related alkanes
Related compounds
 2-Chloroethanol
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

It was invented for use in fire extinguishers by the Germans 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. CBM 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

Its 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]

In fiction

In the Enter the Matrix video game, the player can find a "Chloro-Bromo Methane Gun", which is used as a fire extinguisher. It fires a pressurized cartridge of CBM gas to put out fires. However, due to its chemical properties, firing a cartridge near people causes their lungs to fill with liquid, effectively drowning them.

References
  1. NIOSH Pocket Guide to Chemical Hazards. "#0123". National Institute for Occupational Safety and Health (NIOSH).
  2. "Chlorobromomethane". Immediately Dangerous to Life and Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
  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.
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