Dibromomethane

Dibromomethane
Names
IUPAC name
Dibromomethane[1]
Other names
  • Methyl dibromide
  • Methylene bromide
  • Methylene dibromide
  • Refrigerant-30B2
Identifiers
3D model (JSmol)
Abbreviations
  • DBM
  • MDB
  • UN 2664
969143
ChEBI
ChemSpider
ECHA InfoCard 100.000.750
EC Number
  • 200-824-2
25649
MeSH methylene+bromide
RTECS number
  • PA7350000
UNII
UN number 2664
Properties
CH2Br2
Molar mass 173.835 g·mol−1
Appearance Colorless liquid
Density 2.477 g mL−1
Melting point −52.70 °C; −62.86 °F; 220.45 K
Boiling point 96 to 98 °C; 205 to 208 °F; 369 to 371 K
12.5 g L−1 (at 20 °C)
Vapor pressure 4.65 kPa (at 20.0 °C)
9.3 μmol Pa−1 kg−1
-65.10·10−6 cm3/mol
1.541
Thermochemistry
104.1 J K−1 mol−1
Hazards
GHS pictograms
GHS Signal word Warning
H332, H412
P273
NFPA 704 (fire diamond)
Flammability code 0: Will not burn. E.g. waterHealth code 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
0
2
0
Lethal dose or concentration (LD, LC):
  • 1 g kg−1 (oral, rabbit)
  • 3.738 g kg−1 (subcutaneous, mouse)
  • >4 g kg−1 (dermal, rabbit)
Related compounds
Related alkanes
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

Preparation

Dibromomethane is prepared commercially from dichloromethane via bromochloromethane:

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

The latter route requires aluminium trichloride as a catalyst.[2] The bromochloromethane product from either reaction can further react in a similar manner:

6 CH2BrCl + 3 Br2 + 2 Al → 6 CH2Br2 + 2 AlCl3
CH2BrCl + HBr → CH2Br2 + HCl

In the laboratory, it is prepared from bromoform:

CHBr3 + Na3AsO3 + NaOH → CH2Br2 + Na3AsO4 + NaBr

using sodium arsenite and sodium hydroxide.[3]

Another way is to prepare it from diiodomethane and bromine.

Uses

Dibromomethane is used as a solvent, gauge fluid, and in organic synthesis.[2] It is a convenient agent for converting catechols to their methylenedioxy derivatives.

Natural occurrence

It is naturally produced by marine algae and liberated to the oceans. Releasing on soil causes it to evaporate and leach into the ground. Releasing in water causes it to be lost mainly by volatilisation with a half life of 5.2 hours. It has no significant degradation biological or abiological effects. In the atmosphere it will be lost because of reaction with photochemically produced hydroxyl radicals. The estimated half life of this reaction is 213 days.

References
  • Podsiadlo M.; Dziubek K.; Szafranski M.; Katrusiak A. (December 2006). "Molecular interactions in crystalline dibromomethane and diiodomethane, and the stabilities of their high-pressure and low-temperature phases". Acta Crystallogr. B. 62 (6): 1090–1098(9). doi:10.1107/S0108768106034963. PMID 17108664. Retrieved 2007-06-29.
  1. "methylene bromide - Compound Summary". PubChem Compound. USA: National Center for Biotechnology Information. 25 March 2005. Identification. Retrieved 18 June 2012.
  2. 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.
  3. W. W. Hartman, E. E. Dreger (1929). "Methylene bromide". Org. Synth. 9: 56. doi:10.15227/orgsyn.009.0056.
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