Hydrogen Bromide
Title: Hydrogen Bromide
CAS Registry Number: 10035-10-6
CAS Name: Anhydrous hydrobromic acid
Molecular Formula: BrH
Molecular Weight: 80.91
Percent Composition: Br 98.76%, H 1.25%
Line Formula: HBr
Literature References: Prepd commercially by direct combination of the elements at 375° preferably over a catalyst such as platinized silica gel or platinized asbestos: Richards, Hönigschmid, J. Am. Chem. Soc. 32, 1581 (1910); Smyth, Hitchcock, ibid. 55, 1830 (1933); Schneider, Johnson, Inorg. Synth. 1, 152 (1939). Lab procedure from tetrahydronaphthalene and bromine: Müller, Monatsh. Chem. 49, 29 (1928); Duncan, Inorg. Synth. 1, 151 (1939); Schmeisser in Handbook of Preparative Inorganic Chemistry vol. 1, G. Brauer, Ed. (Academic Press, New York, 2nd ed., 1963) pp 282-286. Detailed description of laboratory methods of prepn: Houben-Weyl, Methoden der organischen Chemie vol 5/4 (Thieme, Stuttgart, 4th ed., 1960) p 16-20. Review of prepn and properties of HBr and other hydrogen halides: Woolf in Mellor's vol. II, Suppl I (originally published as Suppl II, part 1) 724-741 (1956); John in Bromine and its Compounds, Z. E. Jolles, Ed. (Ernest Benn, London, 1966) pp 81-105; Downs, Adams in Comprehensive Inorganic Chemistry vol. 2, J. C. Bailar, Jr. et al., Eds. (Pergamon Press, Oxford, 1973) pp 1280-1329.
Properties: Colorless, corrosive, nonflammable gas. Acrid odor. Fumes in moist air forming clouds which have a sour taste. d 2.71 (air = 1.00). mp -86.9°. bp760 -66.8°; bp11.0 atm -4.8°; bp17.1 atm 12°; bp30.0 atm 36°; bp59.2 atm 70°. Crit temp 89.8°; crit press. 84.5 atm. Sp heat (cal/g/°C): solid (-91°) 0.152; liq 0.176; gas (27°) 0.085. Heat of fusion at mp: 7.44 cal/g. Heat of vaporization at bp: 51.3 cal/g. Freely sol in water: One vol H2O dissolves 600 vols HBr gas at 0°. Also sol in alc. Soly in organic solvents: Fernandes, J. Chem. Eng. Data 17, 377 (1972); Gerrard, Chem. Ind. (London) 1969, 295; Ahmed et al., J. Appl. Chem. 20, 109 (1970). Aq solns are strongly acid. The satd aq soln contains 68.85% HBr at 0° and 66% at 25°. The boiling point of a constant-boiling mixture is 122.5° at 740 mm and 126° at 760 mm. The composition of the constant-boiling mixture is 47.38% HBr at 752 mm. For complete tables see Bonner et al., J. Am. Chem. Soc. 55, 1406 (1943). See also Hydrobromic Acid. Anhydr HBr is marketed in steel cylinders in the form of a gas over liquid. LC50 in mice, rats: 814, 2858 ppm by inhalation, K. C. Back et al., Reclassification of Materials Listed as Transportation Health Hazards (TSA-20-72-3, PB 214-270, 1972).
Melting point: mp -86.9°
Boiling point: bp760 -66.8°; bp11.0 atm -4.8°; bp17.1 atm 12°; bp30.0 atm 36°; bp59.2 atm 70°
Density: d 2.71 (air = 1.00)
Toxicity data: LC50 in mice, rats: 814, 2858 ppm by inhalation, K. C. Back et al., Reclassification of Materials Listed as Transportation Health Hazards (TSA-20-72-3, PB 214-270, 1972)
CAUTION: Potential symptoms of overexposure are irritation of eyes, skin, nose and throat; direct contact with solutions may cause skin and eye burns; direct contact with liquid may cause frostbite. See NIOSH Pocket Guide to Chemical Hazards (DHHS/NIOSH 97-140, 1997) p 166.
Use: Mfg organic and inorganic bromides, hydrobromic acid, as reducing agent and as catalyst in controlled oxidations, in the alkylation of aromatic compds, in the isomerization of conjugated diolefins.

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