Bromine monochloride, also called bromine(I) chloride, bromochloride, and bromine chloride, is an interhalogen inorganic compound with chemical formula BrCl. It is a very reactive golden yellow gas with boiling point 5 °C and melting point −66 °C. Its CAS number is 13863-41-7, and its EINECS number is 237-601-4. It is a strong oxidizing agent. Its molecular structure in the gas phase was determined by microwave spectroscopy; the Br-Cl bond has a length of re = 2.1360376(18) Å. Its crystal structure was determined by single crystal X-ray diffraction; the bond length in the solid state is 2.179(2) Å and the shortest intermolecular interaction is r(Cl···Br) = 3.145(2) Å.

Uses

Bromine monochloride is used in analytical chemistry in determining low levels of mercury, to quantitatively oxidize mercury in the sample to Hg(II) state. A common use of bromine monochloride is as an algaecide, fungicide, and disinfectant of industrial recirculating cooling water systems. Addition of bromine monochloride is used in some types of Li-SO2 batteries to increase voltage and energy density.