Dibromomethane
Spacefill model for dibromomethane
Names
Preferred IUPAC name
Dibromomethane[1]
Other names
  • Methyl dibromide
  • Methylene bromide
  • Methylene dibromide
  • Refrigerant-30B2[citation needed]
Identifiers
3D model (JSmol)
Abbreviations
969143
ChEBI
ChemSpider
ECHA InfoCard 100.000.750 Edit this at Wikidata
EC Number
  • 200-824-2
25649
MeSH methylene+bromide
RTECS number
  • PA7350000
UNII
UN number 2664
  • InChI=1S/CH2Br2/c2-1-3/h1H2 checkY
    Key: FJBFPHVGVWTDIP-UHFFFAOYSA-N checkY
  • BrCBr
Properties
CH2Br2
Molar mass 173.835 g·mol−1
Appearance Colorless to yellow 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 labelling:
GHS07: Exclamation mark
Warning
H332, H412
P273
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformFlammability 0: Will not burn. E.g. waterInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
2
0
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).
checkY verify (what is checkY☒N ?)

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.

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

  1. ^ "methylene bromide - Compound Summary". PubChem Compound. USA: National Center for Biotechnology Information. 25 March 2005. Identification. Retrieved 18 June 2012.
  2. ^ a b 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. ^ W. W. Hartman, E. E. Dreger (1929). "Methylene bromide". Org. Synth. 9: 56. doi:10.15227/orgsyn.009.0056.