出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2012/04/27 19:17:14」(JST)
| Hydrogen bromide | |
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Preferred IUPAC name
Hydrogen bromide[citation needed] |
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Systematic name
Bromane[1] |
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| Identifiers | |
| CAS number | 10035-10-6 Y |
| PubChem | 260 |
| ChemSpider | 255 Y |
| EC number | 233-113-0 |
| UN number | 1048 |
| KEGG | C13645 N |
| MeSH | Hydrobromic+Acid |
| ChEBI | CHEBI:47266 Y |
| ChEMBL | CHEMBL1231461 N |
| RTECS number | MW3850000 |
| Beilstein Reference | 3587158 |
| Jmol-3D images | Image 1 |
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SMILES
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InChI
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| Properties | |
| Molecular formula | HBr |
| Molar mass | 80.91 g mol−1 |
| Exact mass | 79.926162679 g mol-1 |
| Appearance | Colorless gas |
| Odor | Acrid |
| Density | 3.307 g/dm3 |
| Melting point |
-86.9 °C, 186 K, -124 °F |
| Boiling point |
-66.8 °C, 206 K, -88 °F |
| Solubility in water | 221 g/100 mL (0 °C) 204 g/100 mL (15 °C) |
| Solubility | soluble in alcohol, organic solvents |
| Vapor pressure | 2.308 MPa (at 21 °C) |
| Acidity (pKa) | ~–9 [2] |
| Basicity (pKb) | ~23 |
| Refractive index (nD) | 1.325 |
| Structure | |
| Molecular shape | Linear |
| Dipole moment | 820 mD |
| Thermochemistry | |
| Std enthalpy of formation ΔfH |
-36.45--36.13 kJ mol-1[3] |
| Standard molar entropy S |
198.696-198.704 J K-1 mol-1[3] |
| Specific heat capacity, C | 350.7 mJ K-1 g-1 |
| Hazards | |
| MSDS | hazard.com physchem.ox.ac.uk |
| GHS pictograms | |
| GHS signal word | DANGER |
| GHS hazard statements | H314, H335 |
| GHS precautionary statements | P261, P280, P305+351+338, P310 |
| EU Index | 035-002-00-0 |
| EU classification | C |
| R-phrases | R35, R37 |
| S-phrases | (S1/2), S7/9, S26, S45 |
| NFPA 704 |
0
3
0
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| Related compounds | |
| Related compounds | Hydrogen chloride Hydrogen fluoride |
| N (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
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| Infobox references | |
Hydrogen bromide is the diatomic molecule HBr. HBr is a gas at standard conditions. Hydrobromic acid forms upon dissolving HBr in water. Conversely, HBr can be liberated from hydrobromic acid solutions with the addition of a dehydration agent, but not by distillation. Hydrogen bromide and hydrobromic acid are, therefore, not the same, but they are related. Commonly, chemists refer to hydrobromic acid as "HBr", and this usage, while understood by most chemists, is imprecise and can be confusing to the non-specialist.
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At room temperature, HBr is a nonflammable gas with an acrid odor, fuming in moist air because of the formation of hydrobromic acid. HBr is very soluble in water, forming hydrobromic acid solution, which is saturated at 68.85% HBr by weight at room temperature. Aqueous solutions that are 47.38% HBr by weight form a constant-boiling mixture (reverse azeotrope) that boils at 126°C. Boiling less concentrated solutions releases H2O until the constant boiling mixture composition is reached.
There are many uses of HBr in chemical synthesis. For example, HBr is used for the production of alkyl bromides from alcohols:
HBr adds to alkenes to give bromoalkanes, an important family of organobromine compounds:
HBr adds to alkynes to yield bromoalkenes. The stereochemistry of this type of addition is usually anti:
HBr adds to the haloalkene to form a geminal dihaloalkane. (This type of addition follows Markovnikov's rule):
Also, HBr is used to open epoxides and lactones and in the synthesis of bromoacetals. Additionally, HBr catalyzes many organic reactions.[4][5][6][7]
HBr has been proposed for use in a utility-scale flow-type battery.[8]
Hydrogen bromide (along with hydrobromic acid) is produced on a much smaller scale than the corresponding chlorides. In the primary industrial preparation, hydrogen and bromine are combined at temperatures between 200-400 °C. The reaction is typically catalyzed by platinum or asbestos.[5][9]
HBr can be synthesized by a variety of methods. It may be prepared in the laboratory by distillation of a solution of sodium or potassium bromide with phosphoric acid or diluted sulfuric acid[10]:
Concentrated sulfuric acid is ineffective because HBr formed will be oxidized to bromine gas:
The acid may be prepared by several other methods, as well, including reaction of bromine either with phosphorus and water, or with sulfur and water[11]:
Alternatively, it can be prepared by the bromination of tetraline (1,2,3,4-tetrahydronaphthalene):[12]
Alternatively bromine can be reduced with phosphorous acid:[5]
Anhydrous hydrogen bromide can also be produced on a small scale by thermolysis of triphenylphosphonium bromide in refluxing xylene.[4]
HBr prepared by the above methods can be contaminated with Br2, which can be removed by passing the gas through Cu turnings or through phenol.[9]
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| リンク元 | 「hydrobromide」「臭化水素酸」「hydrobromic acid」 |
| 関連記事 | 「bromide」「bromides」 |