Triethylborane

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Triethylborane
Identifiers
CAS number97-94-9 YesY
PubChem7357
ChemSpider7079 YesY
EC number202-620-9
Jmol-3D imagesImage 1
Properties
Molecular formulaC6H15B
Molar mass98.00 g/mol
AppearanceColorless to pale yellow liquid
Density0.677 g/cm3
Melting point−93 °C; −135 °F; 180 K
Boiling point95 °C; 203 °F; 368 K
Solubility in waterN/A, Highly reactive
Hazards
MSDSExternal MSDS
R-phrasesR11 R14/15 R17 R19 R34 R35 R36/37
S-phrasesS6 S7/8 S16 S33 S36/37/39 S43A S45 S29
Main hazardsSpontaneously flammable in air; causes burns
Flash point< 0 °C
Autoignition temperature-20 °C
Related compounds
Related compoundsTetraethyllead
Diborane
Sodium tetraethylborate
trimethylborane
 YesY (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references
 
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Triethylborane
Identifiers
CAS number97-94-9 YesY
PubChem7357
ChemSpider7079 YesY
EC number202-620-9
Jmol-3D imagesImage 1
Properties
Molecular formulaC6H15B
Molar mass98.00 g/mol
AppearanceColorless to pale yellow liquid
Density0.677 g/cm3
Melting point−93 °C; −135 °F; 180 K
Boiling point95 °C; 203 °F; 368 K
Solubility in waterN/A, Highly reactive
Hazards
MSDSExternal MSDS
R-phrasesR11 R14/15 R17 R19 R34 R35 R36/37
S-phrasesS6 S7/8 S16 S33 S36/37/39 S43A S45 S29
Main hazardsSpontaneously flammable in air; causes burns
Flash point< 0 °C
Autoignition temperature-20 °C
Related compounds
Related compoundsTetraethyllead
Diborane
Sodium tetraethylborate
trimethylborane
 YesY (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references

Triethylborane (TEB), also called triethylboron, is an organoborane (a compound with a B-C bond). It is a colorless pyrophoric liquid. Its chemical formula is (C2H5)3B, abbreviated Et3B. It is soluble in organic solvents tetrahydrofuran and hexane.

Preparation and structure[edit]

Triethylborane is prepared by the reaction of trimethyl borate with triethylaluminium:[1]

Et3Al + (MeO)3B → Et3B + "(MeO)3Al"

The molecule is monomeric, unlike H3B and Et3Al, which tend to dimerize. It has a planar BC3 core.[1]

Applications[edit]

Rockets[edit]

Triethylborane was used to ignite the JP-7 fuel in the Pratt & Whitney J58 turbojet/ramjet engines powering the Lockheed SR-71 Blackbird spy plane,[2] and its predecessor A-12 OXCART. Mixed with 10-15% triethylaluminium, it was also used before lift-off to ignite the F-1 Engines on the Saturn V Rocket.[3] Triethylborane is suitable for this because of its pyrophoric properties, especially the fact that it burns with very high temperature. It was chosen as an ignition method for reliability reasons, and in the case of the Blackbird, because the JP-7 fuel has very low volatility and is difficult to ignite. Conventional ignition plugs posed too high risk of a malfunction. It was used to start up each engine and to light the afterburners.[4]

The SpaceX Falcon 9 heavy-lift rocket uses a triethylaluminum-triethylborane mixture as a first-stage ignitor.[5]

Organic chemistry[edit]

Industrially, triethylborane is used as an initiator in radical reactions, where it is effective even at low temperatures.[1] As an initiator, it can replace some organotin compounds.

It reacts with metal enolates, yielding enoxytriethylborates that can be C-alkylated more selectively than in its absence. It is used in the Barton–McCombie deoxygenation reaction for deoxygenation of alcohols. In combination with lithium tri-tert-butoxyaluminum hydride it cleaves ethers. For example, THF is converted, after hydrolysis, to butanol. It also promotes certain variants of the Reformatskii reaction.[6]

It is the precursor to the reducing agent Superhydride:

LiH + Et3B → LiBHEt3

Safety[edit]

Triethylborane is strongly pyrophoric, igniting spontaneously in air, burning with an apple-green flame characteristic for boron compounds. Thus, it must be handled and stored with Nitrogen or Argon.

See also[edit]

References[edit]

  1. ^ a b c Robert J. Brotherton, C. Joseph Weber, Clarence R. Guibert, John L. Little "Boron Compounds" in Ullmann's Encyclopedia of Industrial Chemistry 2000, Wiley-VCH. doi:10.1002/14356007.a04_309
  2. ^ "Lockheed SR-71 Blackbird". March Field Air Museum. Retrieved 2009-05-05. 
  3. ^ A. Young (2008). The Saturn V F-1 Engine: Powering Apollo Into History. Springer. p. 86. ISBN 0-387-09629-9. 
  4. ^ "Lockheed SR-71 Blackbird Flight Manual". www.sr-71.org. Retrieved 2011-01-26. 
  5. ^ Mission Status Center, June 2, 2010, 1905 GMT, SpaceflightNow, accessed 2010-06-02, Quotation: "The flanges will link the rocket with ground storage tanks containing liquid oxygen, kerosene fuel, helium, gaseous nitrogen and the first stage ignitor source called triethylaluminum-triethylborane, better known as TEA-TAB."
  6. ^ Yoshinori Yamamoto, Takehiko Yoshimitsu, John L. Wood, Laura Nicole Schacherer "Triethylborane" Encyclopedia of Reagents for Organic Synthesis. doi:10.1002/047084289X.rt219.pub3