Hydrobromic acid is a

strong acid Acid strength is the tendency of an acid, symbolised by the chemical formula HA, to dissociate into a proton, H+, and an anion, A-. The dissociation of a strong acid in solution is effectively complete, except in its most concentrated solutions ...

formed by dissolving the diatomic molecule

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 ...

(HBr) in water. "Constant boiling" hydrobromic acid is an aqueous solution that distills at and contains 47.6% HBr by mass, which is 8.77 mol/L. Hydrobromic acid has a p''K''_a of −9, making it a stronger acid than

hydrochloric acid Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungent smell. It is classified as a strong acid Acid strength is the tendency of an acid, symbol ...

, but not as strong as

hydroiodic acid Hydroiodic acid (or hydriodic acid) is an aqueous solution of hydrogen iodide (HI). It is a strong acid, one that is ionized completely in an aqueous solution. It is colorless. Concentrated solutions are usually 48% to 57% HI. Reactions Hy ...

. Hydrobromic acid is one of the strongest

mineral acid A mineral acid (or inorganic acid) is an acid derived from one or more inorganic compounds, as opposed to organic acids which are acidic, organic compounds. All mineral acids form hydrogen ions and the conjugate base when dissolved in water. Cha ...

s known.

Uses

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 compound Organobromine compounds, also called organobromides, are organic compounds that contain carbon Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons avai ...

s. 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. HBr almost uniquely participates in anti-Markovnikov hydrohalogenation of alkenes. The resulting 1-bromoalkanes are versatile

alkylating agent Alkylation is the transfer of an alkyl group from one molecule to another. The alkyl group may be transferred as an alkyl carbocation, a free radical, a carbanion, or a carbene (or their equivalents). Alkylating agents are reagents for effectin ...

s, giving rise to fatty amines and quaternary ammonium salts.

Synthesis

Hydrobromic acid can be prepared in the laboratory via the reaction of Br₂, SO₂, and water. :Br₂ + SO₂ + 2 H₂O → H₂SO₄ + 2 HBr More typically laboratory preparations involve 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

phosphorus Phosphorus is a chemical element with the symbol P and atomic number 15. Elemental phosphorus exists in two major forms, white phosphorus and red phosphorus, but because it is highly reactive, phosphorus is never found as a free element on Ear ...

and water. However, it can also be produced electrolytically. It can also be prepared by treating bromides with non-oxidising acids like phosphoric or acetic acids. Alternatively the acid can be prepared with dilute (5.8 M) sulfuric acid and potassium bromide: :H₂SO₄ + KBr → KHSO₄ + HBr Using more concentrated sulfuric acid or allowing the reaction solution to exceed 75 °C further oxidizes HBr to bromine gas. The acid is further purified by filtering out the KHSO₄ and by distilling off the water until the solution reaches an

azeotrope An azeotrope () or a constant heating point mixture is a mixture of two or more liquids whose proportions cannot be altered or changed by simple distillation.Moore, Walter J. ''Physical Chemistry'', 3rd e Prentice-Hall 1962, pp. 140–142 This ...

(≈ 126 °C at 760

torr The torr (symbol: Torr) is a unit of pressure based on an absolute scale, defined as exactly of a standard atmosphere (). Thus one torr is exactly (≈ ). Historically, one torr was intended to be the same as one " millimeter of merc ...

). The yield is approximately 85%. Hydrobromic acid is available commercially in various concentrations and purities.

References

External links

International Chemical Safety Card 0282

*Carlin, W. W. Bromides Nonmetal halides Mineral acids {{DEFAULTSORT:Hydrobromic Acid pl:Bromowodór#Kwas bromowodorowy