Pyridinium perbromide

Pyridinium perbromide (also called pyridinium bromide perbromide, pyridine hydrobromide perbromide, or pyridinium tribromide) is an organic chemical composed of a pyridinium cation and a tribromide anion. It can also be considered as a complex containing pyridinium bromide—the salt of pyridine and hydrogen bromide—with an added bromine (Br₂). The chemical is a solid whose reactivity is similar to that of bromine. It is thus a strong oxidizing agent used as a source of electrophilic bromine in halogenation reactions.^[1] The analogous quinoline compound behaves similarly.^[2]

Pyridinium perbromide

Identifiers
CAS Number	39416-48-3 Y
3D model (JSmol)	Interactive image
ECHA InfoCard	100.049.479
PubChem CID	11983801
UNII	W0AF353S0O Y
CompTox Dashboard (EPA)	DTXSID80885771
InChI InChI=1S/C5H5N.Br3/c1-2-4-6-5-3-1;1-3-2/h1-5H;/q+1;-1 Key: XGXACOWIBOWGSS-UHFFFAOYSA-N
SMILES [n+]1ccccc1.Br[Br-]Br
Properties
Chemical formula	C5H6Br3N
Molar mass	319.822 g·mol−1
Appearance	red crystalline solid
Solubility in water	virtually insoluble
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Preparation

Pyridinium tribromide can be obtained by reacting pyridinium bromide with bromine or thionyl bromide.^[3]

Properties

Pyridinium tribromide is a red crystalline solid^[1] which is virtually insoluble in water.^[4]

Use

Pyridinium tribromide is used as a brominating agent of ketones, phenols, and ethers.^[4] As a stable solid, it can be more easily handled and weighed precisely, especially important properties for use in small scale reactions. One example from the original publications on this chemical is the bromination of the 3-ketosteroid 1 to 2,4-dibromocholestanone (2):^[1]

Bromination of a 3-Ketosteroid.