Zinc bromide is an inorganic compound with the chemical formula ZnBr2. It consists of zinc cations (Zn2+) and bromide anions (Br−) and commonly occurs as colorless, crystalline solids or clear dense solutions. In solid form it is hygroscopic and tends to absorb water; in water or polar solvents it ionizes and forms hydrated zinc complexes. For general reference see additional notes and the entry on chemical formulae.

Physical and chemical characteristics

Zinc bromide is typically highly soluble in water and many polar organic solvents. The salt can form hydrates and complex ions in solution. It behaves as a Lewis acid in organic reactions, accepting electron pairs from donors, and its solutions are electrically conductive because of mobile ions. The solid-state arrangement involves zinc coordinated to bromide ligands in extended arrays rather than simple isolated molecules; on melting or in dilute solution it dissociates to give Zn2+ and Br− species. See also chemical properties.

Preparation and historical notes

Commercial zinc bromide is made by reacting metallic zinc or zinc oxide with hydrobromic acid, or by controlled combination of zinc and bromine under suitable conditions. Historically, zinc halides have been studied for their reactivity and use as reagents in laboratory chemistry; the bromide salt became more prominent where the larger halide size or greater solubility than the chloride were advantageous.

Uses and applications

  • Laboratory reagent and catalyst: used as a Lewis-acid catalyst in some organic transformations and as a source of zinc(II) and bromide in synthesis.
  • Energy storage: employed as an electrolyte in zinc–bromine flow batteries because of its redox-active bromide and zinc species.
  • Industrial fluids: concentrated zinc bromide solutions are used as high-density completion and packer fluids in oil and gas well operations where a heavy, clear brine is required.
  • Other uses: occasional applications in specialty chemical processes and research contexts where bromide coordination chemistry is relevant.

For practical application notes consult technical sources such as industry guides.

Safety, handling and environmental aspects

Zinc bromide is corrosive and can cause irritation to skin, eyes and respiratory tissues. Solutions are dense and may pose inhalation or ingestion hazards; disposal and spills should follow local regulations. As with many heavy-metal salts, zinc bromide can be toxic to aquatic organisms in sufficient concentrations, so releases to the environment should be minimized and controlled. Practical safety guidance appears in material safety data resources and supplier documentation, for example safety information.

Distinguishing zinc bromide from related compounds: compared with zinc chloride, the bromide is generally more soluble in some organic solvents and provides different reactivity patterns in coordination and Lewis-acid chemistry because of the larger, more polarizable bromide ion. This influences choice of reagent in synthesis and industrial formulations.