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Boron tribromide

Names
IUPAC name Boron tribromide
Other names Tribromoborane, Boron bromide
Identifiers
CAS Number	10294-33-4
3D model (JSmol)	Interactive image
ChemSpider	16787736
ECHA InfoCard	100.030.585
EC Number	233-657-9
PubChem CID	25134
RTECS number	ED7400000
UNII	A453DV9339
UN number	2692
CompTox Dashboard (EPA)	DTXSID4065028
InChI InChI=1S/B.3BrH/h;3*1H/q+3;;;/p-3Key: LKBREHQHCVRNFR-UHFFFAOYSA-K InChI=1/BBr3/c2-1(3)4Key: ILAHWRKJUDSMFH-UHFFFAOYAA InChI=1/B.3BrH/h;3*1H/q+3;;;/p-3Key: LKBREHQHCVRNFR-DFZHHIFOAX
SMILES BrB(Br)Br
Properties
Chemical formula	BBr3
Molar mass	250.52 g·mol
Appearance	Colorless to amber liquid
Odor	Sharp and irritating
Density	2.643 g/cm
Melting point	−46.3 °C (−51.3 °F; 226.8 K)
Boiling point	91.3 °C (196.3 °F; 364.4 K)
Solubility in water	Reacts violently with water and other protic solvents
Solubility	Soluble in CH2Cl2, CCl4
Vapor pressure	7.2 kPa (20 °C)
Refractive index (nD)	1.00207
Viscosity	7.31 x 10 Pa s (20 °C)
Thermochemistry
Heat capacity (C)	0.2706 J/K
Std molar entropy (S298)	228 J/mol K
Std enthalpy of formation (ΔfH298)	-0.8207 kJ/g
Hazards
Occupational safety and health (OHS/OSH):
Main hazards	Reacts violently with water, potassium, sodium, and alcohols; attacks metals, wood, and rubber
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	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)	3 0 2W
Flash point	Noncombustible
NIOSH (US health exposure limits):
PEL (Permissible)	None
REL (Recommended)	C 1 ppm (10 mg/m)
IDLH (Immediate danger)	N.D.
Safety data sheet (SDS)	ICSC 0230
Related compounds
Related compounds	Boron trifluoride Boron trichloride Boron triiodide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C , 100 kPa). N verify (what is  ?) Infobox references

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.

Chemical properties

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.

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.

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.

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. Boron tribromide also mediates the dealkylation of aryl alkyl ethers, for example demethylation of 3,4-dimethoxystyrene into 3,4-dihydroxystyrene.

Synthesis

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

The first synthesis was done by Poggiale in 1846 by reacting boron trioxide with carbon and bromine at high temperatures:

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:

2 B + 3 Br₂ → 2 BBr₃

Applications

Boron tribromide is used in organic synthesis, pharmaceutical manufacturing, image processing, semiconductor doping, semiconductor plasma etching, and photovoltaic manufacturing.

See also

• List of highly toxic gases

References

1. ^ NIOSH Pocket Guide to Chemical Hazards. "#0061". National Institute for Occupational Safety and Health (NIOSH).
2. "Boron Tribromide". Toxicologic Review of Selected Chemicals. National Institute for Occupational Safety and Health. 2018-09-21.
3. Doyagüez, E. G. (2005). "Boron Tribromide". Synlett. 2005 (10): 1636–1637. doi:10.1055/s-2005-868513.
4. 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.
5. 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.
6. 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.
7. 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.
8. Wöhler, F.; Deville, H. E. S.-C. (1858). "Du Bore". Annales de Chimie et de Physique. 52: 63–92.
9. Akira Suzuki, Shoji Hara, Xianhai Huang (2006). "Boron Tribromide". Encyclopedia of Reagents for Organic Synthesis. doi:10.1002/047084289X.rb244.pub2. ISBN 978-0471936237. {{cite book}}: |journal= ignored (help)CS1 maint: multiple names: authors list (link)

Further reading

• Doyagüez, E. G. (2005). "Boron Tribromide". Synlett. 2005 (10): 1636–1637. doi:10.1055/s-2005-868513.

External links

• 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 

• Boron compounds
• Bromides
• Boron halides
• Acid catalysts