Preferred IUPAC name
Systematic IUPAC name
ECHA InfoCard 100.030.090
3.307 g/mL (25 °C)
-86.9 °C (-124.4 °F; 186.2 K)
-66.8 °C (-88.2 °F; 206.3 K)
221 g/100 mL (0 °C) 204 g/100 mL (15 °C) 193 g/100 mL (20 °C) 130 g/100 mL (100 °C)
Soluble in alcohol, organic solvents
2.308 MPa (at 21 °C)
Acidity (p K a)
-8.8 (±0.8); ~-9 
Basicity (p K b)
Safety data sheet
GHS Signal word
P261, P280, P305+351+338, P310
Lethal dose or concentration (LD, LC):
2858 ppm (rat, 1 h) 814 ppm (mouse, 1 h)
(US health exposure limits):
TWA 3 ppm (10 mg/m 3)
TWA 3 ppm (10 mg/m 3)
Hydrogen fluoride Hydrogen chloride Hydrogen iodide Hydrogen astatide
Except where otherwise noted, data are given for materials in their
(at 25 °C [77 °F], 100 kPa).
( verify what is ?)
Hydrogen bromide is the inorganic compound with the formula H Br . 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 temperature. Aqueous solutions that are 47.6% HBr by mass form a constant-boiling azeotrope mixture that boils at 124.3 °C. Boiling less concentrated solutions releases H 2O until the constant-boiling mixture composition is reached.
Hydrogen bromide, and its aqueous solution, are commonly used reagents in the preparation of bromide compounds.
Hydrogen bromide and hydrobromic acid are important reagents in the production of
organobromine compounds.   In a  free-radical reaction, HBr adds to alkenes:
RCH=CH 2 + HBr -> R-CHBr-CH 3
The resulting alkyl bromides are useful
alkylating agents, e.g., as precursors to fatty amine derivatives. Relaated free radical additions to allyl chloride and styrene give 1-bromo-3-chloropropane and phenylethylbromide, respectively.
Hydrogen bromide reacts with
dichloromethane to give bromochloromethane and dibromomethane, sequentially:
HBr + CH
2Cl 2 -> HCl + CH 2BrCl HBr + CH 2BrCl -> HCl + CH 2Br 2
These metathesis reactions illustrate the consumption of the stronger acid (HBr) and release of the weaker acid (HCl).
Allyl bromide is prepared by treating allyl alcohol with HBr:
CH 2=CHCH 2OH + HBr -> CH 2=CHCH 2Br + H 2O
HBr adds to
alkynes to yield bromoalkenes. The stereochemistry of this type of addition is usually anti:
RC?CH + HBr -> RC(Br)=CH 2
Also, HBr adds
epoxides and lactones, resulting in ring-opening.
triphenylphosphine, HBr gives triphenylphosphonium bromide, a solid "source" of HBr.
P(C 6H 5) 3 + HBr -> [HP(C 6H 5) 3] +Br -
Vanadium(III) bromide and molybdenum(IV) bromide were prepared by treatment of the higher chlorides with HBr. These reactions proceed via redox reactions:
2 VCl 4 + 8 HBr -> 2 VBr 3 + 8 HCl + Br 2
Hydrogen bromide (along with hydrobromic acid) is produced by combining
hydrogen and bromine at temperatures between 200 and 400 °C. The reaction is typically catalyzed by platinum or asbestos. 
HBr can be prepared by distillation of a solution of
sodium bromide or potassium bromide with phosphoric acid or sulfuric acid:
KBr + H 2SO 4 -> KHSO 4 + HBr
Concentrated sulfuric acid is less effective because it oxidizes HBr to
2 HBr + H 2SO 4 -> Br 2 + SO 2 + 2 H 2O
The acid may be prepared by:
reaction of bromine with water and
 2 Br 2 + S + 2 H 2O -> 4 HBr + SO 2 bromination of
 C 10H 12 + 4 Br 2 -> C 10H 8Br 4 + 4 HBr reduction of bromine with phosphorous acid:
 Br 2 + H 3PO 3 + H 2O -> H 3PO 4 + 2 HBr
Anhydrous hydrogen bromide can also be produced on a small scale by
thermolysis of triphenylphosphonium bromide in refluxing xylene.
Hydrogen bromide prepared by the above methods can be contaminated with Br
2, which can be removed by passing the gas through a solution of phenol at room temperature in tetrachloromethane or other suitable solvent (producing 2,4,6-tribromophenol and generating more HBr in the process) or through copper turnings or copper gauze at high temperature.
HBr is highly corrosive and irritating to inhalation.
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Lide, David R., ed. (2006). (87th ed.). Boca Raton, FL: CRC Handbook of Chemistry and Physics CRC Press. ISBN . 0-8493-0487-3
Trummal, Aleksander; Lipping, Lauri; Kaljurand, Ivari; Koppel, Ilmar A; Leito, Ivo (2016). "Acidity of Strong Acids in Water and Dimethyl Sulfoxide". The Journal of Physical Chemistry A. 120 (20): 3663-9. Bibcode: 2016JPCA..120.3663T. doi: 10.1021/acs.jpca.6b02253. PMID 27115918.
^ Perrin, D. D. Dissociation constants of inorganic acids and bases in aqueous solution. Butterworths, London, 1969.
^ a b
Zumdahl, Steven S. (2009). Chemical Principles 6th Ed. Houghton Mifflin Company. ISBN . 978-0-618-94690-7
^ a b c
NIOSH Pocket Guide to Chemical Hazards. "#0331". National Institute for Occupational Safety and Health (NIOSH).
"Hydrogen bromide". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
Dagani, M. J.; Barda, H. J.; Benya, T. J.; Sanders, D. C. "Bromine Compounds". . Weinheim: Wiley-VCH. Ullmann's Encyclopedia of Industrial Chemistry doi: 10.1002/14356007.a04_405. CS1 maint: multiple names: authors list ( link)
^ a b c Greenwood, N. N.; Earnshaw, A. Chemistry of the Elements; Butterworth-Heineman: Oxford, Great Britain; 1997; pp. 809-812.
^ Vollhardt, K. P. C.;
Schore, N. E. Organic Chemistry: Structure and Function; 4th Ed.; W. H. Freeman and Company: New York, NY; 2003.
^ a b Hercouet, A.; LeCorre, M. (1988) Triphenylphosphonium bromide: A convenient and quantitative source of gaseous hydrogen bromide. Synthesis, 157-158.
Calderazzo, Fausto; Maichle-Mössmer, Cäcilie; Pampaloni, Guido; Strähle, Joachim (1993). "Low-Temperature Syntheses of Vanadium(III) and Molybdenum(IV) Bromides by Halide Exchange". J. Chem. Soc., Dalton Trans. (5): 655-658. doi: 10.1039/DT9930000655.
^ a b Ruhoff, J. R.; Burnett, R. E.; Reid, E. E.
"Hydrogen Bromide (Anhydrous)" Organic Syntheses, Vol. 15, p. 35 (Coll. Vol. 2, p. 338).
^ a b c M. Schmeisser "Chlorine, Bromine, Iodine" in Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 282.