Selenium Monobromide, Se₂Br₂

Selenium Monobromide, Se₂Br₂, is produced together with the tetrabromide by the action of boiling bromine on selenium. The reaction, which is accompanied by considerable heat evolution, may be moderated by dissolving the bromine in carbon disulphide. The substance can also be produced by treating the tetrabromide with selenium at the ordinary temperature.

It is a very deep red liquid having a density of 3.60 at 15° C.; its odour is unpleasant. It is soluble in carbon disulphide and in chloroform and is, in its turn, a solvent for selenium. When heated, partial decomposition occurs, with formation of bromine and the tetrabromide, distillation taking place at 225° C.

The action of water on selenium monobromide is analogous to the action on the corresponding chlorine compound, selenium and selenium dioxide being formed.

Combination with bromine readily occurs, with production of the tetrabromide.

Selenium monobromide reacts with gaseous ammonia in a similar way to the corresponding chloride. With liquid ammonia in the presence of ether, it gives the compound Se₂N₂Br.

From the fact that on reacting with organo-magnesium compounds selenium monobromide gives rise to organic substances containing a chain linking, -Se-Se- , it is probable that the constitution is to be represented by Br-Se-Se-Br.