Selenium Oxybromide, SeOBr₂

Selenium Oxybromide, SeOBr₂, may be prepared by adding the calculated amount of fused selenium to pure selenium dioxide in a cooled flask and dropping in the requisite quantity of bromine slowly. The mixture is then warmed until the whole of the oxide has dissolved.

The oxybromide is a reddish-yellow solid, melting at 41.5° C. It has a boiling-point of 217° C. at 740 mm., with considerable decomposition. It decomposes so readily on heating that it cannot be purified by distillation even under reduced pressure. Its electrical conductivity is 6×10^-5 mho at 40° to 50° C.

It is slowly converted by water into a mixture of selenious and hydrobromic acids. It is soluble in carbon disulphide, chloroform, benzene, toluene, xylene and carbon tetrachloride.

Selenium oxybromide is a very active chemical agent. It reacts with sulphur in the cold with the evolution of sulphur dioxide, and with selenium to form the monobromide. Phosphorus reacts violently with the solid; silicon and carbon are unattacked.

The majority of the metals react with selenium oxybromide with the production of the corresponding metal bromides, selenium dioxide and selenium monobromide. Zinc, cadmium, chromium, nickel, cobalt, tungsten and tantalum, however, are not attacked even after prolonged heating at 100° C.

Potassium chlorate liberates bromine from the oxybromide, whilst potassium perchlorate, permanganate, dichromate and chromium trioxide are without action on it.

By bubbling dry air at 60° C. through the oxybromide, bromine is liberated; this is stated by Lenher to be due to a primary dissociation into the dioxide and tetrabromide, followed by a secondary dissociation of the tetrabromide into the monobromide and bromine.

Carbon monoxide and sulphur dioxide have no action on the oxybromide.