Carbonyl bromide

Carbonyl bromide, also known as bromophosgene, is a carbon oxohalide and a bromine analogue of phosgene, with the chemical formula COBr2. It is a colorless liquid. Carbonyl bromide is a decomposition product of halon compounds used in fire extinguishers.

Synthesis and reactions
Carbonyl bromide is formed by the oxidation carbon tetrabromide with sulfuric acid:
 * CBr4 + H2SO4 → COBr2 + SO2 + Br2 + H2O

In contrast to phosgene, carbonyl bromide cannot be produced efficiently by halogenation of carbon monoxide. The bromination of carbon monoxide follows this equation:
 * CO + Br2 ⇌ COBr2

But the process is slow at room temperature. Increasing temperature, in order to increase the reaction rate, results in a further shift of the chemical equilibrium towards the educts (since ΔRH < 0 and ΔRS < 0).

Carbonyl bromide slowly decomposes to carbon monoxide and elemental bromine even at low temperatures. It is also sensitive to hydrolysis, breaking down into hydrogen bromide, water and carbon dioxide.