Dibromomethane

Dibromomethane

Dibromomethane

Chemical compound

Dibromomethane or methylene bromide, or methylene dibromide is a halomethane with the formula CH2Br2. It is slightly soluble in water but very soluble in organic solvents. It is a colorless liquid.

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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 using sodium arsenite and sodium hydroxide:[3]

CHBr3 + Na3AsO3 + NaOH → CH2Br2 + Na3AsO4 + NaBr


Another way is to prepare it from diiodomethane and bromine.

Uses

Dibromomethane is used as a solvent, gauge fluid, and in organic synthesis (often as 1H-NMR internal standard).[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. [1]
    "methylene bromide - Compound Summary". PubChem Compound. USA: National Center for Biotechnology Information. 25 March 2005. Identification. Retrieved 18 June 2012.
  2. [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. ISBN 978-3527306732.
  3. [3]
    W. W. Hartman, E. E. Dreger (1929). "Methylene bromide". Org. Synth. 9: 56. doi:10.15227/orgsyn.009.0056.
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