Boron tribromide: Difference between revisions

{{Short description|Chemical compound}}

| Verifiedfields = changed

| verifiedrevid = 441021200

| Name = Boron tribromide

| ImageFile = Boron-tribromide-3D-vdW.png

| ImageName = Boron tribromide

| ImageFile1 = BBr3.jpg

| ImageName1 = Sample of boron tribromide

| IUPACName = Boron tribromide

| OtherNames = Tribromoborane, Boron bromide

|Section1={{Chembox Identifiers

| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}

| CASNo_Ref = {{cascite|correct|CAS}}

| UNII_Ref = {{fdacite|changed|FDA}}

| UNII = A453DV9339

| PubChem = 25134

| RTECS = ED7400000

| EINECS = 233-657-9

| UNNumber = 2692

|Section2={{Chembox Properties

| B=1|Br=3

| Appearance = Colorless to amber liquid

| Odor = Sharp and irritating<ref name=PGCH/>

| Density = 2.643 g/cm³

| Solubility = Reacts violently with water and other protic solvents

| SolubleOther = Soluble in [[dichloromethane|CH₂Cl₂]], [[carbon tetrachloride|CCl₄]]

| MeltingPtC = −46.3

| BoilingPtC = 91.3

| VaporPressure = 7.2 kPa (20 °C)

| Viscosity = 7.31 x 10⁻⁴ Pa s (20 °C)

| RefractIndex = 1.00207

|Section4={{Chembox Thermochemistry

| DeltaHc =

| DeltaGf =

| Entropy = 228 J/mol K

|Section7={{Chembox Hazards

| ExternalSDS = [http://www.inchem.org/documents/icsc/icsc/eics0230.htm ICSC 0230]

| GHSPictograms = {{GHS06|Acute Tox. 2}}{{GHS05|Skin Corr. 1B}}

| GHSSignalWord = DANGER

| HPhrases = {{H-phrases|330|300|314}} Within the European Union, the following additional hazard statement (EUH014) must also be displayed on labeling: Reacts violently with water.

| NFPA-H = 3

| NFPA-F = 0

| NFPA-R = 2

| NFPA-S = W

| FlashPt_notes= Noncombustible<ref name=PGCH/>

| PEL = None<ref name=PGCH>{{PGCH|0061}}</ref>

| REL = C 1 ppm (10 mg/m³)<ref name=PGCH/>

| IDLH = N.D.<ref name=PGCH/>

| MainHazards = Reacts violently with water, potassium, sodium, and alcohols; attacks metals, wood, and rubber<ref name=PGCH/>

|Section8={{Chembox Related

| OtherCompounds = [[Boron trifluoride]]<br />[[Boron trichloride]]<br />[[Boron triiodide]]

'''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.<ref>{{ cite web | publisher = National Institute for Occupational Safety and Health | url = https://www.cdc.gov/niosh/pel88/10294-33.html | work = Toxicologic Review of Selected Chemicals | title = Boron Tribromide | date = 2018-09-21 }}</ref>

Boron tribromide is commercially available and is a strong [[Lewis acid]].

It is an excellent demethylating or dealkylating agent for the [[Bond cleavage|cleavage]] of [[ether]]s, also with subsequent cyclization, often in the production of [[medication|pharmaceuticals]].<ref name=doya>{{ cite journal | title = Boron Tribromide | author = Doyagüez, E. G. | journal = Synlett | year = 2005 | volume = 2005 | issue = 10 | pages = 1636–1637 | doi = 10.1055/s-2005-868513 | doi-access = free }}</ref>

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.<ref name=sousa>{{ cite journal | title = BBr₃-Assisted Cleavage of Most Ethers Does Not Follow the Commonly Assumed Mechanism |author1=Sousa, C. |author2=Silva, P.J. |name-list-style=amp | journal = Eur. J. Org. Chem. | year = 2013 | volume = 2013| issue = 23 | pages = 5195–5199| doi = 10.1002/ejoc.201300337 | hdl = 10284/7826 |s2cid=97825780 | hdl-access = free }}</ref>

: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.<ref name=McOmie>{{ cite journal | title = Demethylation of Aryl Methyl Ethers by Boron Tribromide |author1=McOmie, J. F. W. |author2=Watts, M. L. |author3=West, D. E. | journal = Tetrahedron | year = 1968 | volume = 24 | issue = 5 | pages = 2289–2292 | doi = 10.1016/0040-4020(68)88130-X }}</ref>

:ROBBr₂ + 3H₂O → ROH + B(OH)₃ + 2HBr

It also finds applications in [[olefin]] [[polymer]]ization 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 (semiconductor)|doping]] in the manufacture of [[semiconductors]].<ref>{{ cite journal |author1=Komatsu, Y. |author2=Mihailetchi, V. D. |author3=Geerligs, L. J. |author4=van Dijk, B. |author5=Rem, J. B. |author6=Harris, M. | title = Homogeneous p⁺ emitter diffused using borontribromide for record 16.4% screen-printed large area n-type mc-Si solar cell | journal = Solar Energy Materials and Solar Cells | year = 2009 | volume = 93 | issue = 6–7 | pages = 750–752 | doi = 10.1016/j.solmat.2008.09.019 }}</ref>

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&nbsp;°C leads to the formation of boron tribromide. The product can be purified by vacuum [[distillation]].

The first synthesis was done by [[Antoine Baudoin Poggiale|Poggiale]] in 1846 by reacting boron trioxide with carbon and bromine at high temperatures:<ref>{{ cite journal | title = Nouveau composé de brome et de bore, ou acide bromoborique et bromoborate d'ammoniaque | author = Poggiale, M. | journal = Comptes Rendus Hebdomadaires des Séances de l'Académie des Sciences | volume = 22 | pages = 124–130 | year = 1846 | url = http://gallica.bnf.fr/ark:/12148/bpt6k29798/f128.table }}</ref>

:B₂O₃ + 3 C + 3 Br₂ → 2 BBr₃ + 3 CO

An improvement of this method was developed by [[Friedrich Wöhler|F. Wöhler]] and [[Henri Etienne Sainte-Claire Deville|Deville]] in 1857. By starting from amorphous boron the reaction temperatures are lower and no carbon monoxide is produced:<ref>{{ cite journal | title = Du Bore | author1 = Wöhler, F. | author-link1 = Friedrich Wöhler | author2 = Deville, H. E. S.-C. | author-link2 = Henri Etienne Sainte-Claire Deville | journal = [[Annales de Chimie et de Physique]] | volume = 52 | pages = 63–92 | year = 1858 | url = http://gallica.bnf.fr/ark:/12148/bpt6k347939/f62.table }}</ref>

==Applications==

Boron tribromide is used in organic synthesis,<ref>{{cite book | chapter = Boron Tribromide | author = Akira Suzuki, Shoji Hara, Xianhai Huang | title = Encyclopedia of Reagents for Organic Synthesis | doi = 10.1002/047084289X.rb244.pub2 | journal = E-EROS Encyclopedia of Reagents for Organic Synthesis| year = 2006 | isbn = 978-0471936237 }}</ref> pharmaceutical manufacturing, image processing, semiconductor doping, semiconductor plasma etching, and photovoltaic manufacturing.

{{Reflist}}

* {{cite journal | title = Boron Tribromide | author = Doyagüez, E. G. | journal = Synlett | year = 2005 | volume = 2005 | issue = 10 | pages = 1636–1637 | doi = 10.1055/s-2005-868513 | doi-access = free }}

* [http://www.periodicvideos.com/videos/mv_boron_tribromide.htm Boron Tribromide] at ''[[The Periodic Table of Videos]]'' (University of Nottingham)

* [https://www.cdc.gov/niosh/npg/npgd0061.html NIOSH Pocket Guide to Chemical Hazards - Boron Tribromide] (Centers for Disease Control and Prevention)

* {{ cite web | url = http://fscimage.fishersci.com/msds/96654.htm | title = Material Safety Data Sheet – Boron tribromide | publisher = Fisher Science }}

* {{ cite patent | country = US | status = patent | number = 2989375 | title = Production of Boron Tribromide | inventor = May, F. H.; Bradford, J. L. | assign1 = American Potash & Chemical | gdate = 1961-06-20 }}

{{bromides}}

{{bromine compounds}}

[[Category:Acid catalysts]]