Phosphoryl Dichlorobromide, POCl₂Br

Phosphoryl Dichlorobromide, POCl₂Br, was made by passing a mixture of HBr and the vapour of POCl₃ through a glass tube at 400° to 500° C., and also by the action of PBr₅ on P₂O₃Cl₄ (q.v.). A good yield is obtained from the halogenated alkyl derivatives. Phosphoryl ethyl dichloride when treated with bromine gives ethyl bromide and POCl₂Br. Phosphoryl ethoxydichloride, which may be obtained from alcohol and P₂O₃Cl₄, is acted upon by PBr₅ according to the equation

PO(OC₂H₅)Cl₂ + PBr₅ = POCl₂Br + POBr₃ + C₂H₅Br

The formula was established by analysis and by the determination of vapour density. The density is 2.12065 at 0° C. and 1.83844 at the boiling-point, 137.6° C. The coefficient of expansion is expressed by the equation

v_t = v₀(1 + 0.00100518t + 0.0₆49053t² + 0.0₈44065t³)

The solid melts at 11° to 13° C.

The chemical properties are similar to those of POCl₃. When heated the compound dissociates into POCl₃ and POBr₃.