Iron(III) bromide explained

Iron(III) bromide is the chemical compound with the formula FeBr₃. 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.

Structure, synthesis and basic properties

FeBr₃ forms a polymeric structure featuring six-coordinate, octahedral Fe centers.^[1] Although inexpensively available commercially, FeBr₃ can be prepared by treatment of iron metal with bromine:

2 Fe + 3 Br₂ → 2 FeBr₃

Above 200 °C, FeBr₃ decomposes to ferrous bromide:

2FeBr₃ → 2FeBr₂ + Br₂Iron(III) chloride is considerably more stable, reflecting the greater oxidizing power of chlorine. FeI₃ is not stable, as iron(III) will oxidize iodide ions.

Uses

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.^[2]

See also

• Iron(II) bromide, the lower bromide of iron

Notes and References

1. Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. .
2. Iron(III) bromide. Drapeau, Martin Pichette . Lafantaisie, Mathieu . Ollevier, Thierry . E-EROS Encyclopedia of Reagents for Organic Synthesis. 2013. 10.1002/047084289X.rn01568. 978-0471936237.