Hydrogen bromide

  • Formula: HBr
  • Hill system formula: Br1H1
  • CAS registry number: [10035-10-6]
  • Formula weight: 80.912
  • Class: bromide
  • Colour: colourless
  • Appearance: gas
  • Melting point: -88.6°C
  • Boiling point: -67°C
  • Density: 2603 kg m-3 (liquid near freezing point); 3.55 kg m-3 (gas)

The following are some synonyms of hydrogen bromide:

  • hydrogen bromide
  • hydrogen(I) bromide
  • hyrobromic acid

The oxidation number of hydrogen in hydrogen bromide is 1.


Hydrogen bromide gas can be made in the laboratory by the bromination of tetralin (1,2,3,4-tetrahydronapthalene). The downside is that half of the bromine is lost. The yield is about 94% (that is, 47% of the bromine ends up as HBr).

C10H12 + 4Br2 → C10H8Br4 + 4HBr

Hydrogen bromide gas may also be made in the laboratory by the reaction of concentrated sulphuric acid upon sodium bromide. However, a lot of the product is lost by oxidation with excess sulphuric acid to form bromine and sulphur dioxide.

NaBr(s) + H2SO4 → HBr(g) + NaHSO4(s)

Hydrogen bromide may be made in the laboratory by the reaction between purified hydrogen gas and bromine. This is catalyzed by platinized asbestos and carried out in a quartz tube at 250°C.

Br2 + H2 [Pt] → 2HBr

Solid state structure

  • Geometry of hydrogen: 1 coordinate: terminus
  • Prototypical structure:

Crystal structure of hydrogen bromide

Element analysis

The table shows element percentages for HBr (hydrogen bromide).

Element %
Br 98.75
H 1.25

Isotope pattern for HBr

The chart below shows the calculated isotope pattern for the formula HBr with the most intense ion set to 100%.


The data on these compounds pages are assembled and adapted from the primary literature and several other sources including the following.

  • R.T. Sanderson in Chemical Periodicity, Reinhold, New York, USA, 1960.
  • N.N. Greenwood and A. Earnshaw in Chemistry of the Elements, 2nd edition, Butterworth, UK, 1997.
  • F.A. Cotton, G. Wilkinson, C.A. Murillo, and M. Bochmann, in Advanced Inorganic Chemistry, John Wiley & Sons, 1999.
  • A.F. Trotman-Dickenson, (ed.) in Comprehensive Inorganic Chemistry, Pergamon, Oxford, UK, 1973.
  • R.W.G. Wyckoff, in Crystal Structures, volume 1, Interscience, John Wiley & Sons, 1963.
  • A.R.West in Basic solid state chemistry Chemistry, John Wiley & Sons, 1999.
  • A.F. Wells in Structural inorganic chemistry, 4th edition, Oxford, UK, 1975.
  • J.D.H. Donnay, (ed.) in Crystal data determinative tables, ACA monograph number 5, American Crystallographic Association, USA, 1963.
  • D.R. Lide, (ed.) in Chemical Rubber Company handbook of chemistry and physics, CRC Press, Boca Raton, Florida, USA, 77th edition, 1996.
  • J.W. Mellor in A comprehensive treatise on inorganic and theoretical chemistry, volumes 1-16, Longmans, London, UK, 1922-1937.
  • J.E. Macintyre (ed.) in Dictionary of inorganic compounds, volumes 1-3, Chapman & Hall, London, UK, 1992.

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