Iron(III) bromide is the chemical compound with the formula FeBr<sub>3</sub>. Also known as ferric bromide, this red-brown odorless compound is used as a Lewis acid catalyst in the halogenation of aromatic compounds. It dissolves in water to give acidic solutions.
FeBr<sub>3</sub> forms a polymeric structure featuring six-coordinate, octahedral Fe centers. Although inexpensively available commercially, FeBr<sub>3</sub> can be prepared by treatment of iron metal with bromine:
Above 200 ðC, FeBr<sub>3</sub> decomposes to ferrous bromide:
Iron(III) chloride is considerably more stable, reflecting the greater oxidizing power of chlorine. FeI<sub>3</sub> is not stable, as iron(III) will oxidize iodide ions.
Ferric bromide is occasionally used as an oxidant in organic chemistry, e.g. for the conversion of alcohols to ketones. It is used as a Lewis acidic catalyst for bromination of aromatic compounds. For the latter applications, it is often generated in situ.