Chemistry:Dibromomethane

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Dibromomethane
Natta projection of dibromomethane.svg
Spacefill model for dibromomethane
Names
Preferred IUPAC name
Dibromomethane[1]
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
Tracking categories (test):

|Section1=! colspan=2 style="background: #f8eaba; text-align: center;" |Identifiers

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3D model (JSmol)

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| 969143 |- | ChEBI

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| ChemSpider

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| EC Number

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  • 200-824-2

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| 25649 |-


| MeSH | methylene+bromide |-

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|- | RTECS number

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  • PA7350000

|- | UNII

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|- | UN number | 2664 |-

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|- |Section2=! colspan=2 style="background: #f8eaba; text-align: center;" |Properties

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| 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

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| 12.5 g⋅L−1 (at 20 °C) |-





| Vapor pressure | 4.65 kPa (at 20.0 °C) |-

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| 9.3 μmol⋅Pa−1⋅kg−1 |-






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| −65.10·10−6⋅cm3/mol |-

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| 1.541 |- |Section3=! colspan=2 style="background: #f8eaba; text-align: center;" |Thermochemistry

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| 104.1 J⋅K−1⋅mol−1 |- |Section4=! colspan=2 style="background: #f8eaba; text-align: center;" |Hazards

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| GHS pictograms | GHS07: Harmful |- | GHS Signal word |WARNING

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| H332, H412 |-

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| P273 |-



| NFPA 704 (fire diamond)

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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 codeNFPA 704 four-colored diamond
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2
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| colspan=2 style="text-align:left; background-color:#f1f1f1;" | Lethal dose or concentration (LD, LC): |-

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  • 1 g⋅kg−1 (oral, rabbit)
  • 3.738 g⋅kg−1 (subcutaneous, mouse)
  • >4 g⋅kg−1 (dermal, rabbit)

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|- |Section5=! colspan=2 style="background: #f8eaba; text-align: center;" |Related compounds

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Related alkanes

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|- }} 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. https://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=3024&loc=ec_rcs#x291. 
  2. 2.0 2.1 Dagani, M. J.; Barda, H. J.; Benya, T. J.; Sanders, D. C.. "Ullmann's Encyclopedia of Industrial Chemistry". 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. 

External links