Dibromine trioxide is the chemical compound composed of bromine and oxygen with the formula Br<sub>2</sub>O<sub>3</sub>. It is an orange solid that is stable below −40 ðC. It has the structure Br−O−BrO<sub>2</sub> (bromine bromate). It was discovered in 1993. The bond angle of Br−O−Br is 111.7ð, the bond angle of O−Br=O is 103.1ð, and the bond angle of O=Br=O is 107.6ð. The Br−OBrO<sub>2</sub> bond length is 1.845 ÃÂ, the O−BrO<sub>2</sub> bond length is 1.855 àand the Br=O bond length is 1.612 à.
Dibromine trioxide can be prepared by reacting a solution of bromine in dichloromethane with ozone at low temperatures. It disproportionates in alkali solutions to Br and BrO.