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 of carbon tetrabromide with sulfuric acid: In contrast to phosgene, carbonyl bromide cannot be produced efficiently by halogenation of carbon monoxide. The bromination of carbon monoxide follows this equation: 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 and carbon dioxide.