Bromine trifluoride
# Bromine trifluoride

Bromine trifluoride is an interhalogen compound with the formula $BrF_3.$ At room temperature, it is a straw-coloured liquid with a pungent odor which decomposes violently on contact with water and organic compounds. It is a powerful fluorinating agent and an ionizing inorganic solvent. It is used to produce uranium hexafluoride $(UF_6)$ in the processing and reprocessing of nuclear fuel.

## Synthesis

Bromine trifluoride was first described by Paul Lebeau in 1906, who obtained the material by the reaction of bromine with fluorine at 20 °C:

    $Br_2$ + 3 $F_2$ → 2 $BrF_3$

The disproportionation of bromine monofluoride also gives bromine trifluoride:

    3 BrF → $BrF_3$ + $Br_2$

## Structure

Like $ClF_3$ and $IF_3,$ the $BrF_3$ molecule is T-shaped and planar. In the VSEPR formalism, the bromine center is assigned two electron pairs. The distance from the bromine each axial fluorine is 1.81 Å and to the equatorial fluorine is 1.72 Å. The angle between an axial fluorine and the equatorial fluorine is slightly smaller than 90° — the 86.2° angle observed is due to the repulsion generated by the electron pairs being greater than that of the Br-F bonds.

## Chemical properties

In a highly exothermic reaction, $BrF_3$ reacts with water to form hydrobromic acid and hydrofluoric acid:

    $BrF_3$ + 2 $H_2O$ → 3 HF + HBr + $O_2$

$BrF_3$ is a fluorinating agent, but less reactive than $ClF_3.$ Already at -196 °C, it reacts with acetonitrile to give 1,1,1-trifluoroethane.

    $BrF_3$ + $CH_3CN$ → $CH_3CF_3$ + 1⁄2 $Br_2$ + 1⁄2 $N_2$

The liquid is conducting, owing to autoionisation:

    2 $BrF_3$ ⇌ BrF+2 + BrF−4

Fluoride salts dissolve readily in $BrF_3$ forming tetrafluorobromate:

    KF + $BrF_3$ → $KBrF_4$

It reacts as a fluoride donor:

    $BrF_3$ + $SbF_5$ → [BrF+2][SbF−6]
