Boron tribromide
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| Names | |
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IUPAC name
Boron tribromide
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| Other names
Tribromoborane, Boron bromide
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| Identifiers | |
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3D model (Jmol)
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| ChemSpider | |
| ECHA InfoCard | 100.030.585 |
| EC Number | 233-657-9 |
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PubChem CID
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| RTECS number | ED7400000 |
| UNII | |
| UN number | 2692 |
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| Properties | |
| BBr3 | |
| Molar mass | 250.52 g/mol |
| Appearance | colorless to amber liquid |
| Odor | sharp and irritating |
| Density | 2.643 g/cm3 |
| Melting point | −46.3 °C (−51.3 °F; 226.8 K) |
| Boiling point | 91.3 °C (196.3 °F; 364.4 K) |
| reacts violently | |
| Solubility | soluble in ethanol, CCl4 |
| Vapor pressure | 7.2 kPa (20 °C) |
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Refractive index (nD)
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1.00207 |
| Viscosity | 7.31 x 10−4 Pa s (20 °C) |
| Thermochemistry | |
| 0.2706 J/K | |
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Std molar
entropy (S |
228 J/mol K |
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Std enthalpy of
formation (ΔfH |
-0.8207 kJ/g |
| Hazards | |
| Main hazards | reacts violently with water, potassium, sodium, and alcohols; attacks metals, wood, and rubber |
| Safety data sheet | ICSC 0230 |
| GHS pictograms |
 
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| GHS signal word | DANGER |
| H330, H300, H314 Within the European Union, the following additional hazard statement (EUH014) must also be displayed on labelling: Reacts violently with water. | |
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EU classification (DSD)
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Very toxic (T+) Corrosive (C) |
| R-phrases | R14, R26/28, R35 |
| S-phrases | (S1/2), S9, S26, S28, S36/37/39, S45 |
| NFPA 704 | |
| Flash point | noncombustible |
| US health exposure limits (NIOSH): | |
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PEL (Permissible)
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none |
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REL (Recommended)
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C 1 ppm (10 mg/m3) |
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IDLH (Immediate danger)
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N.D. |
| Related compounds | |
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Related compounds
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Boron trifluoride Boron trichloride Boron triiodide |
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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 (what is   ?) |
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| Infobox references | |
Boron tribromide, BBr3, is a colorless, fuming liquid compound containing boron and bromine. It is decomposed by water and alcohols.
Boron tribromide is commercially available and is a strong Lewis acid.
It is an excellent demethylating or dealkylating agent for the cleavage of ethers, also with subsequent cyclization, often in the production of pharmaceuticals.
The mechanism of dealkylation of tertiary alkyl ethers proceeds via the formation of a complex between the boron center and the ether oxygen followed by the elimination of an alkyl bromide to yield a dibromo(organo)borane.
Aryl methyl ethers (as well as activated primary alkyl ethers), on the other hand are dealkylated through a bimolecular mechanism involving two BBr3-ether adducts.
The dibromo(organo)borane can then undergo hydrolysis to give a hydroxyl group, boric acid, and hydrogen bromide as products.
It also finds applications in olefin polymerization and in Friedel-Crafts chemistry as a Lewis acid catalyst.
The electronics industry uses boron tribromide as a boron source in pre-deposition processes for doping in the manufacture of semiconductors. Boron tribromide also mediates the dealkylation of aryl alkyl ethers, for example demethylation of 3,4-dimethoxystyrene into 3,4-dihydroxystyrene.
The reaction of boron carbide with bromine at temperatures above 300 °C leads to the formation of boron tribromide. The product can be purified by vacuum distillation.
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