Hydrogen bromide is a colorless gas with the chemical formula HBr, consisting of one hydrogen atom bonded to one bromine atom. First prepared in 1809 by French chemist Louis-Joseph Gay-Lussac, this corrosive compound dissolves readily in water to form hydrobromic acid, one of the strongest mineral acids known. With its sharp, irritating odor and tendency to form white fumes in moist air, hydrogen bromide serves as a crucial reagent in organic chemistry for adding bromine atoms to molecules and as a catalyst in petroleum refining. Despite being less common than its chlorine cousin (HCl), hydrogen bromide’s unique reactivity makes it indispensable for producing pharmaceuticals, flame retardants, and specialty chemicals, though its corrosive nature and ability to damage respiratory tissues require sophisticated handling systems in the thousands of tons produced globally each year.

Find a review of the 50 most important industrial gases here.

20 Fun Facts About Hydrogen Bromide

Beyond the basics above, what else should we know about Hydrogen Bromide? Check out the 20 fun facts below!

1. HBr forms the strongest hydrohalic acid when dissolved in water, even stronger than hydrochloric acid due to bromine’s larger size.
2. The gas liquefies at -66.8°C, forming a clear liquid that can cause severe frostbite and chemical burns simultaneously.
3. Hydrogen bromide molecules rotate 10¹¹ times per second at room temperature, creating a characteristic microwave spectrum.
4. Medieval alchemists unknowingly produced HBr by heating bromide salts with sulfuric acid, calling the fumes “spirit of sea salt.”
5. The compound’s boiling point is 122°C higher than HCl despite similar structures, due to stronger intermolecular forces.
6. HBr catalyzes the isomerization of butane to isobutane at oil refineries, improving octane ratings in gasoline.
7. The gas has a dipole moment of 0.82 Debye, making it less polar than water but more polar than hydrogen chloride.
8. Volcanic gases contain trace HBr from seawater bromine reacting with volcanic HCl and sulfur compounds at high temperatures.
9. Hydrogen bromide etches silicon wafers 50 times faster than HCl, enabling precise semiconductor manufacturing processes.
10. The molecule’s bond length is exactly 1.414 Angstroms, serving as a reference standard in spectroscopy studies.
11. Antarctic ozone holes worsen when HBr releases bromine radicals on ice crystal surfaces during polar spring.
12. The pharmaceutical industry uses 40% of global HBr production for removing protecting groups in drug synthesis.
13. HBr gas glows purple when electrically excited, used in some specialized discharge lamps for spectroscopy.
14. Anhydrous hydrogen bromide costs about $500 per kilogram due to difficult handling and purification requirements.
15. The compound forms azeotropes with water at 47.6% HBr, boiling constantly at 124.3°C regardless of distillation.
16. Free radical bromination using HBr and peroxides follows “anti-Markovnikov” addition, opposite to normal ionic reactions.
17. Hydrogen bromide sensors use silver electrodes that darken from AgBr formation, detecting leaks at 3 ppm.
18. The gas dissolves endothermically in water, actually cooling the solution despite forming a strong acid.
19. UV light decomposes HBr into hydrogen and bromine atoms, creating a purple color from free bromine.
20. Hydrogen bromide forms clathrate hydrates with water at high pressure, trapping HBr molecules in ice cages.

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