Dibromomethane

Dibromomethane
IUPAC name Dibromomethane
Other names Methylene bromide, Methylene dibromide, Methyl dibromide, DBM, MDB, Refrigerant-30B2, UN 2664
Identifiers
CAS number	74-95-3 Y
PubChem	3024
ChemSpider	2916 Y
EC number	200-824-2
ChEBI	CHEBI:47077 Y
RTECS number	PA7350000
Jmol-3D images	Image 1
SMILES BrCBr
InChI InChI=1S/CH2Br2/c2-1-3/h1H2 Y Key: FJBFPHVGVWTDIP-UHFFFAOYSA-N Y InChI=1/CH2Br2/c2-1-3/h1H2 Key: FJBFPHVGVWTDIP-UHFFFAOYAK
Properties
Molecular formula	CH2Br2
Molar mass	173.83 g/mol
Appearance	Clear colorless to yellowish heavy liquid of low viscosity
Density	2.4970 g/cm3 at 20 °C 2.477 g/cm3 at 25 °C
Melting point	-52.7 °C
Boiling point	96.95 °C
Solubility in water	12.5 g/l at 20 °C
Vapor pressure	60 hPa at 20 °C
Hazards
EU classification	Harmful (Xn), Dangerous for the environment (N)
R-phrases	R20 R52/53
S-phrases	(S2) S24 S61
NFPA 704	0 2 0
Flash point	None
Y (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Dibromomethane or methylene bromide, or methylene dibromide is a halomethane. It is slightly soluble in water, but very soluble in carbon tetrachloride, diethyl ether and methanol. Its refractive index is 1.5419 (20 °C, D).

Preparation

Dibromomethane can be prepared from bromoform by reaction

CHBr₃ + Na₃AsO₃ + NaOH → CH₂Br₂ + Na₃AsO₄ + NaBr

using sodium arsenite and sodium hydroxide.^[1]

Another way is to prepare it from diiodomethane and bromine.

Uses

Dibromomethane is used as a solvent, gage fluid, and in organic synthesis.

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 degradating 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 Cryst. B62 (6): 1090–1098(9). doi:10.1107/S0108768106034963. PMID 17108664. http://scripts.iucr.org/cgi-bin/paper?bk5037. Retrieved 2007-06-29. 

1. ^ Methylene bromide preparation

External links

• International Chemical Safety Card 0354
• Pesticide residues in food 1979 - Dibromomethane
• MSDS at Oxford University