Dibromomethane

Dibromomethane or methylene bromide, or methylene dibromide is a halomethane. It is slightly soluble in water, but very soluble in carbon tetrachloride, 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.

Other way is to prepare it from diiodomethane and bromine.

Uses
Methylene bromide 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 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. Estimate half life of this reaction is 213 days.