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 | |
3D model (JSmol)
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| ChemSpider | |
| ECHA InfoCard | 100.030.585 |
| EC Number |
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PubChem CID
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| RTECS number |
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| UNII | |
| UN number | 2692 |
CompTox Dashboard (EPA)
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| Properties | |
| BBr3 | |
| Molar mass | 250.52 g·mol−1 |
| Appearance | Colorless to amber liquid |
| Odor | Sharp and irritating[1] |
| 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 with water and other protic solvents | |
| Solubility | Soluble in CH2Cl2, CCl4 |
| Vapor pressure | 7.2 kPa (20 °C) |
Refractive index (nD)
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1.00207 |
| Viscosity | 7.31 x 10−4 Pa s (20 °C) |
| Thermochemistry | |
Heat capacity (C)
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0.2706 J/K |
Std molar
entropy (S⦵298) |
228 J/mol K |
Std enthalpy of
formation (ΔfH⦵298) |
-0.8207 kJ/g |
| Hazards | |
| Occupational safety and health (OHS/OSH): | |
Main hazards
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Reacts violently with water, potassium, sodium, and alcohols; attacks metals, wood, and rubber[1] |
| GHS labelling: | |
 
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| Danger | |
| H300, H314, H330 Within the European Union, the following additional hazard statement (EUH014) must also be displayed on labeling: Reacts violently with water. | |
| NFPA 704 (fire diamond) | |
| Flash point | Noncombustible[1] |
| NIOSH (US health exposure limits): | |
PEL (Permissible)
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None[1] |
REL (Recommended)
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C 1 ppm (10 mg/m3)[1] |
IDLH (Immediate danger)
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N.D.[1] |
| Safety data sheet (SDS) | ICSC 0230 |
| Related compounds | |
Related compounds
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Boron trifluoride Boron trichloride Boron triiodide |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Boron tribromide, BBr3, is a colorless, fuming liquid compound containing boron and bromine. Commercial samples usually are amber to red/brown, due to weak bromine contamination. It is decomposed by water and alcohols.[2]
Chemical properties
[edit]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.[3]
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.
- ROR + BBr3 → RO+(−BBr3)R → ROBBr2 + RBr
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.[4]
- RO+(−BBr3)CH3 + RO+(−BBr3)CH3→ RO(−BBr3) + CH3Br + RO+(BBr2)CH3
The dibromo(organo)borane can then undergo hydrolysis to give a hydroxyl group, boric acid, and hydrogen bromide as products.[5]
- ROBBr2 + 3H2O → ROH + B(OH)3 + 2HBr
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.[6] Boron tribromide also mediates the dealkylation of aryl alkyl ethers, for example demethylation of 3,4-dimethoxystyrene into 3,4-dihydroxystyrene.
Synthesis
[edit]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.
History
[edit]The first synthesis was done by Poggiale in 1846 by reacting boron trioxide with carbon and bromine at high temperatures:[7]
- B2O3 + 3 C + 3 Br2 → 2 BBr3 + 3 CO
An improvement of this method was developed by F. Wöhler and Deville in 1857. By starting from amorphous boron the reaction temperatures are lower and no carbon monoxide is produced:[8]
- 2 B + 3 Br2 → 2 BBr3
Applications
[edit]Boron tribromide is used in organic synthesis,[9] pharmaceutical manufacturing, image processing, semiconductor doping, semiconductor plasma etching, and photovoltaic manufacturing.
See also
[edit]References
[edit]- ^ a b c d e f NIOSH Pocket Guide to Chemical Hazards. "#0061". National Institute for Occupational Safety and Health (NIOSH).
- ^ "Boron Tribromide". Toxicologic Review of Selected Chemicals. National Institute for Occupational Safety and Health. 2018-09-21.
- ^ Doyagüez, E. G. (2005). "Boron Tribromide". Synlett. 2005 (10): 1636–1637. doi:10.1055/s-2005-868513.
- ^ Sousa, C. & Silva, P.J. (2013). "BBr3-Assisted Cleavage of Most Ethers Does Not Follow the Commonly Assumed Mechanism". Eur. J. Org. Chem. 2013 (23): 5195–5199. doi:10.1002/ejoc.201300337. hdl:10284/7826. S2CID 97825780.
- ^ McOmie, J. F. W.; Watts, M. L.; West, D. E. (1968). "Demethylation of Aryl Methyl Ethers by Boron Tribromide". Tetrahedron. 24 (5): 2289–2292. doi:10.1016/0040-4020(68)88130-X.
- ^ Komatsu, Y.; Mihailetchi, V. D.; Geerligs, L. J.; van Dijk, B.; Rem, J. B.; Harris, M. (2009). "Homogeneous p+ emitter diffused using borontribromide for record 16.4% screen-printed large area n-type mc-Si solar cell". Solar Energy Materials and Solar Cells. 93 (6–7): 750–752. doi:10.1016/j.solmat.2008.09.019.
- ^ Poggiale, M. (1846). "Nouveau composé de brome et de bore, ou acide bromoborique et bromoborate d'ammoniaque". Comptes Rendus Hebdomadaires des Séances de l'Académie des Sciences. 22: 124–130.
- ^ Wöhler, F.; Deville, H. E. S.-C. (1858). "Du Bore". Annales de Chimie et de Physique. 52: 63–92.
- ^ Akira Suzuki, Shoji Hara, Xianhai Huang (2006). "Boron Tribromide". Encyclopedia of Reagents for Organic Synthesis. doi:10.1002/047084289X.rb244.pub2. ISBN 978-0471936237.
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Further reading
[edit]- Doyagüez, E. G. (2005). "Boron Tribromide". Synlett. 2005 (10): 1636–1637. doi:10.1055/s-2005-868513.
External links
[edit]- Boron Tribromide at The Periodic Table of Videos (University of Nottingham)
- NIOSH Pocket Guide to Chemical Hazards - Boron Tribromide (Centers for Disease Control and Prevention)
- "Material Safety Data Sheet – Boron tribromide". Fisher Science.
- US patent 2989375, May, F. H.; Bradford, J. L., "Production of Boron Tribromide", issued 1961-06-20, assigned to American Potash & Chemical