Pyridinium perbromide (also called pyridinium bromide perbromide, pyridine hydrobromide perbromide, or pyridinium tribromide) is an

organic chemical In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. The ...

composed of a

pyridinium Pyridinium refers to the cation . It is the conjugate acid of pyridine. Many related cations are known involving substituted pyridines, e.g. picolines, lutidines, collidines. They are prepared by treating pyridine with acids. As pyridine is ...

cation and a

tribromide Tribromide is the anion with the chemical formula Br3−, or salts containing it: * Tetrabutylammonium tribromide * Tetrabromophosphonium tribromide * Pyridinium perbromide Sodium and potassium tribromides can be prepared by reacting NaBr or K ...

anion. It can also be considered as a complex containing pyridinium bromide—the salt of

pyridine Pyridine is a basic heterocyclic organic compound with the chemical formula . It is structurally related to benzene, with one methine group replaced by a nitrogen atom. It is a highly flammable, weakly alkaline, water-miscible liquid with a ...

and

hydrogen bromide Hydrogen bromide is the inorganic compound with the formula . It is a hydrogen halide consisting of hydrogen and bromine. A colorless gas, it dissolves in water, forming hydrobromic acid, which is saturated at 68.85% HBr by weight at room tempe ...

—with an added

bromine Bromine is a chemical element with the symbol Br and atomic number 35. It is the third-lightest element in group 17 of the periodic table ( halogens) and is a volatile red-brown liquid at room temperature that evaporates readily to form a simi ...

(Br₂). The chemical is a solid whose reactivity is similar to that of bromine. It is thus a strong

oxidizing Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a d ...

agent used as a source of electrophilic bromine in halogenation reactions. The analogous

quinoline Quinoline is a heterocyclic aromatic organic compound with the chemical formula C9H7N. It is a colorless hygroscopic liquid with a strong odor. Aged samples, especially if exposed to light, become yellow and later brown. Quinoline is only sli ...

compound behaves similarly.

Preparation

Pyridinium tribromide can be obtained by reacting pyridinium bromide with

or thionyl bromide.

Properties

Pyridinium tribromide is a crystalline red solid which is virtually insoluble in water.

Use

Pyridinium tribromide is used as a brominating agent of ketones,

phenols In organic chemistry, phenols, sometimes called phenolics, are a class of chemical compounds consisting of one or more hydroxyl groups (— O H) bonded directly to an aromatic hydrocarbon group. The simplest is phenol, . Phenolic compounds are ...

, and

ethers In organic chemistry, ethers are a class of compounds that contain an ether group—an oxygen atom connected to two alkyl or aryl groups. They have the general formula , where R and R′ represent the alkyl or aryl groups. Ethers can again be ...

.Pyridine hydrobromide perbromide, tech. 90%
data sheet from AlfaAesar, accessed August 13 2017. 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): Bromierung durch Pyridiniumperbromid V2

References

{{reflist Oxidizing agents Pyridinium compounds Bromine compounds Polyhalides