Hydrogen bromide

Description

Hydrobromic Acid is a strong acid formed by dissolving the diatomic molecule HBr in water. “Constant-boiling” hydrobromic acid is an aqueous solution that distills at 124.3°C and contains 47.6% HBr by weight. Hydrobromic acid has a pKa of 9, making it a stronger acid than hydrochloric acid, but not as strong as HI, hydroiodic acid. Hydrobromic acid is one of the strongest mineral acids known.
Hydrobromic acid is mainly used for the production of inorganic bromides, especially the bromides of zinc, calcium, and sodium. It is a useful reagent for generating organobromine compounds. Certain ethers are cleaved with HBr. It also catalyzes alkylation reactions and the extraction of certain ores. Industrially significant organic compounds prepared from hydrobromic acid include allyl bromide, tetrabromobis(phenol), and bromoacetic acid. Hydrobromic acid can be prepared in the laboratory via the reaction of Br2, SO2 and water. Another laboratory preparation involves the production of anhydrous HBr, which is then dissolved in water.
Hydrobromic acid has commonly been prepared industrially by reacting bromine with either sulfur or phosphorous and water. However, it can also be produced electrolytically. It can also be prepared by treating bromides with nonoxidizing acids like phosphoric or acetic acids. Hydrobromic acid is available commercially in various concentrations and purities.

Description

Hydrobromic acid (HBr) is commonly sold as a 48% (by weight) solution in water. HBr works well as a Lewis acid catalyst but the increased nucleophilicity of bromide relative to chloride generally makes hydrochloric acid the preferable choice. However, in certain reactions such as in the deprotection of methyl ethers, the increased nucleophilicity of bromide is advantageous. HBr is also a reasonable choice in reactions where the presence of bromide already exists, such as Sandmeyer reactions and brominations.

The Uses of Hydrogen bromide

Hydrogen bromide is used as a reagent and catalyst in several types of organic reactions such as the formation of alkyl bromides from alcohols.
It is also used as a source material in the preparation of inorganic bromides. Hydrogen bromide serves as a catalyst in alkylation reactions. It has also been reportedly used in the controlled oxidation of aliphatic and alicyclic hydrocarbons to peroxides, ketones, and acids. In organic synthesis, hydrogen bromide is used to substitute bromine for aliphatic chlorine in the presence of aluminum catalyst.

The Uses of Hydrogen bromide

A mixture of the SM (2 g, 5.82 mmol), HBr in AcOH (12 mL), and aq HBr (6 mL) was heated at 100 C for 3 h. The reaction mixture was cooled to RT, extracted with EtOAc (2 x 100 mL), washed with brine, dried (Na2SO4), and concentrated to provide the product as an off-white solid. [1.3 g]