Zinc bromide


Zinc bromide is an inorganic compound with the chemical formula ZnBr2. It is a colourless salt that shares many properties with zinc chloride, namely a high solubility in water forming acidic solutions, and solubility in organic solvents. It is hygroscopic and forms a dihydrate ZnBr2 · 2H2O.

Production

ZnBr2 · 2H2O is prepared by treating zinc oxide or zinc metal with hydrobromic acid.
The anhydrous material can be produced by dehydration of the dihydrate with hot CO2 or by reaction of zinc metal and bromine.

Structure

Crystalline ZnBr2 adopts the same structure as ZnI2: four tetrahedral Zn centers share three vertices to form “super-tetrahedra” of nominal composition 2−, which are linked by their vertices to form a three-dimensional structure. The dihydrate ZnBr2 · 2H2O also has a usual structure and should be described as Zn6 Zn2Br6, where the Zn2Br62− ion has bromine bridges linking the two zinc atoms. A similar structure is found in the dimeric form of aluminium bromide.
Gaseous ZnBr2 is linear in accordance with VSEPR theory with a Zn-Br bond length of 221 pm.

Uses

Zinc bromide is used in the following applications:
Safety considerations are similar to those for zinc chloride, for which the toxic dose for humans is 3–5 g.