Chemistry:Dibromomethane

Dibromomethane

Names
Preferred IUPAC name Dibromomethane
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):

• SizeSet

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

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CAS Number

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• 74-95-3 ^Y

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3D model (JSmol)

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• Interactive image

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Beilstein Reference

| 969143 |- | ChEBI

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• CHEBI:47077 ^Y

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| ChemSpider

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• 2916 ^Y

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| EC Number

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• 200-824-2

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Gmelin Reference

| 25649 |-

| MeSH | methylene+bromide |-

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PubChem CID

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• 3024

|- | RTECS number

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• PA7350000

|- | UNII

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• V69B659W01 ^Y

|- | UN number | 2664 |-

| colspan="2" |

InChI

• InChI=1S/CH2Br2/c2-1-3/h1H2 ^Y

  Key: FJBFPHVGVWTDIP-UHFFFAOYSA-N ^Y

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| colspan="2" |

SMILES

• BrCBr

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

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Chemical formula

| 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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Solubility in water

| 12.5 g⋅L⁻¹ (at 20 °C) |-

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

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Henry's law
constant (k_H)

| 9.3 μmol⋅Pa⁻¹⋅kg⁻¹ |-

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Magnetic susceptibility (χ)

| −65.10·10⁻⁶⋅cm³/mol |-

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Refractive index (n_D)

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

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Heat capacity (C)

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

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| GHS pictograms | |- | GHS Signal word |WARNING

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GHS hazard statements

| H332, H412 |-

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GHS precautionary statements

| P273 |-

| NFPA 704 (fire diamond)

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0

2

0

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

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LD₅₀ (median dose)

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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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• Bromoform
• Tetrabromomethane
• 1,1-Dibromoethane
• 1,2-Dibromoethane

|- }} 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. 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:

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). 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. http://scripts.iucr.org/cgi-bin/paper?bk5037. Retrieved 2007-06-29. 

External links

• International Chemical Safety Card 0354