tribromide

Tribromide is a term used in inorganic and physical chemistry to describe species that contain three bromine atoms in a single unit. The most common example is the tribromide anion Br3−, which forms when bromine (Br2) mixes with bromide (Br−) in solution: Br2 + Br− ⇌ Br3−. In such polyhalide equilibria, the Br3− anion can be viewed as a Br2 molecule interacting with a bromide ion, often described as either Br−–Br–Br or Br2–Br− depending on the model; the true electronic structure is a resonance-stabilized state with delocalized charge over the three bromine atoms. The species is typically formed in concentrated bromide solutions or in the presence of excess Br2 and influences the color and redox properties of the solution.

Tribromide species are primarily discussed in the context of bromide solutions and halogen chemistry, where they participate in redox processes such as oxidation and halogen exchange. They are less stable in strongly acidic or highly oxidizing conditions, where they can be reduced to Br− or oxidize other species depending on the environment.

In practical terms, tribromide ions are analogous to triiodide (I3−) ions and are often mentioned in spectroscopic and analytical contexts, where the presence of Br3− affects absorbance and titration chemistry. Safety considerations follow those of bromine chemistry: bromine is corrosive and vapors are hazardous; polyhalide solutions should be handled with appropriate precautions.