Dibromomethane
Preparation. Dibromomethane is prepared commercially from dichloromethane via bromochloromethane: The latter route requires aluminium trichloride as a catalyst. The bromochloromethane product from either reaction can further react in a similar manner: In the laboratory, it is prepared from bromoform: using sodium arsenite and sodium hydroxide. Another way is to prepare it from diiodomethane and bromine. Uses. Dibromomethane is used as a solvent, gauge fluid, and in organic synthesis. 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.