Triethylborane
Encyclopedia
Triethylborane also called triethylborine and triethylboron, is an organoborane
(an organometallic compound), a near-colorless to yellowish transparent liquid with pungent ether
-like odor. Its chemical formula can be written as C6
H15
B
, or (CH3CH2)3B, or (C2H5)3B, or Et3B.
Triethylborane is strongly pyrophoric, igniting spontaneously in air. It burns intensely with a very hot flame. The color of the flame is apple-green, which is characteristic for boron compounds. Its fire should not be extinguished with water; a carbon dioxide or dry powder extinguisher (e.g. Purple K) would be more suitable. Its vapors may cause flash fire
.
It is soluble in tetrahydrofuran
and hexane
, and is not pyrophoric when in solution. However the solution can slowly react with atmospheric moisture. If the TEB solutions are exposed to air for prolonged time, unstable organic peroxide
s may form, with the presence of cationic initiators leading to polymerization
. It is toxic to peripheral nervous system
, kidneys and testes. Triethylborane is extremely corrosive
. Some sources incorrectly refer to this chemical as tetraethylborane.
fuel in the Pratt & Whitney J58
turbojet/ramjet
engines powering the Lockheed SR-71 Blackbird spy plane, 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. 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. Classical ignition plugs posed too high risk of a malfunction. It was used to start up each engine and to light the afterburner
s.
The SpaceX
Falcon 9
heavy-lift
rocket
uses a triethylaluminum-triethylborane mixture as a first-stage ignitor.
Industrially, triethylborane is used as an initiator
in radical
reactions, where it is effective even at low temperatures. As an initiator, it can replace some organotin
compounds. It reacts with metal enolates, yielding enoxytriethylborates with use in selective alkylation
and aldol
reactions. It is also used in reduction bond cleavage
with lithium tri-tert-butoxyaluminohydride, in preparation of various boron
compounds, deoxygenation
of primary and secondary alcohol
s, rapid determination of -OH
groups in organic compounds, dehydration of salt and sugar hydrate
s, determination of water content in crystalline hydrate compounds, in a variant of Reformatskii reaction
, and has a range of other uses in organoborane chemistry.
Triethylborane is used in vapor deposition
techniques as a boron source. Examples are the plasma deposition of boron-containing hard carbon films, silicon nitride-boron nitride films, and for doping
of diamond
film with boron. Other boron precursors used for such applications are e.g. trimethylborane
, boron trifluoride
, diborane
, and decaborane
.
Sodium tetraethyl borate (NaTEB), a triethylboron derivative, is used as a powerful ethylation agent.
Organoborane
Organoborane or organoboron compounds are chemical compounds that are organic derivatives of BH3, for example trialkyl boranes. Organoboron chemistry or organoborane chemistry is the chemistry of these compounds...
(an organometallic compound), a near-colorless to yellowish transparent liquid with pungent ether
Diethyl ether
Diethyl ether, also known as ethyl ether, simply ether, or ethoxyethane, is an organic compound in the ether class with the formula . It is a colorless, highly volatile flammable liquid with a characteristic odor...
-like odor. Its chemical formula can be written as C6
Carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
H15
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
B
Boron
Boron is the chemical element with atomic number 5 and the chemical symbol B. Boron is a metalloid. Because boron is not produced by stellar nucleosynthesis, it is a low-abundance element in both the solar system and the Earth's crust. However, boron is concentrated on Earth by the...
, or (CH3CH2)3B, or (C2H5)3B, or Et3B.
Triethylborane is strongly pyrophoric, igniting spontaneously in air. It burns intensely with a very hot flame. The color of the flame is apple-green, which is characteristic for boron compounds. Its fire should not be extinguished with water; a carbon dioxide or dry powder extinguisher (e.g. Purple K) would be more suitable. Its vapors may cause flash fire
Flash fire
A flash fire is a sudden, intense fire caused by ignition of a mixture of air and a dispersed flammable substance such as a solid , flammable or combustible liquid , or a flammable gas...
.
It is soluble in tetrahydrofuran
Tetrahydrofuran
Tetrahydrofuran is a colorless, water-miscible organic liquid with low viscosity at standard temperature and pressure. This heterocyclic compound has the chemical formula 4O. As one of the most polar ethers with a wide liquid range, it is a useful solvent. Its main use, however, is as a precursor...
and hexane
Hexane
Hexane is a hydrocarbon with the chemical formula C6H14; that is, an alkane with six carbon atoms.The term may refer to any of four other structural isomers with that formula, or to a mixture of them. In the IUPAC nomenclature, however, hexane is the unbranched isomer ; the other four structures...
, and is not pyrophoric when in solution. However the solution can slowly react with atmospheric moisture. If the TEB solutions are exposed to air for prolonged time, unstable organic peroxide
Organic peroxide
Organic peroxides are organic compounds containing the peroxide functional group . If the R' is hydrogen, the compound is called an organic hydroperoxide. Peresters have general structure RCOOR. The O-O bond easily breaks and forms free radicals of the form RO·...
s may form, with the presence of cationic initiators leading to polymerization
Polymerization
In polymer chemistry, polymerization is a process of reacting monomer molecules together in a chemical reaction to form three-dimensional networks or polymer chains...
. It is toxic to peripheral nervous system
Peripheral nervous system
The peripheral nervous system consists of the nerves and ganglia outside of the brain and spinal cord. The main function of the PNS is to connect the central nervous system to the limbs and organs. Unlike the CNS, the PNS is not protected by the bone of spine and skull, or by the blood–brain...
, kidneys and testes. Triethylborane is extremely corrosive
Corrosive
A corrosive substance is one that will destroy or irreversibly damage another surface or substance with which it comes into contact. The main hazards to people include damage to the eyes, the skin, and the tissue under the skin; inhalation or ingestion of a corrosive substance can damage the...
. Some sources incorrectly refer to this chemical as tetraethylborane.
Applications
Triethylborane was used to ignite the JP-7JP-7
JP-7 is a jet fuel developed by the U.S. Air Force for use in supersonic aircraft because of its high flash point and thermal stability. It is the fuel used in the Pratt & Whitney J58 engines, used in the Lockheed SR-71 Blackbird. The air compression of Mach 3+ cruising flight generates very high...
fuel in the Pratt & Whitney J58
Pratt & Whitney J58
The Pratt & Whitney J58 was a jet engine used on the Lockheed A-12, and subsequently on the YF-12 and SR-71 Blackbird aircraft. The J58 was a variable cycle engine which functioned as both a turbojet and a fan-assisted ramjet. The J58 was a single-spool turbojet engine with an afterburner...
turbojet/ramjet
Ramjet
A ramjet, sometimes referred to as a stovepipe jet, or an athodyd, is a form of airbreathing jet engine using the engine's forward motion to compress incoming air, without a rotary compressor. Ramjets cannot produce thrust at zero airspeed and thus cannot move an aircraft from a standstill...
engines powering the Lockheed SR-71 Blackbird spy plane, and its predecessor A-12 OXCART
A-12 OXCART
The Lockheed A-12 was a reconnaissance aircraft built for the Central Intelligence Agency by Lockheed's famed Skunk Works, based on the designs of Clarence "Kelly" Johnson. The A-12 was produced from 1962 through 1964, and was in operation from 1963 until 1968. The single-seat design, which first...
. Mixed with 10-15% triethylaluminium
Triethylaluminium
Triethylaluminium is an organoaluminium compound. This volatile, colorless liquid is highly pyrophoric, igniting immediately upon exposure to air. It is normally stored in stainless steel containers either as a pure liquid or as a solution in hydrocarbon solvents such as hexane, heptane, or ...
, it was also used before lift-off to ignite the F-1 Engines
F-1 (rocket engine)
The F-1 is a rocket engine developed by Rocketdyne and used in the Saturn V. Five F-1 engines were used in the S-IC first stage of each Saturn V, which served as the main launch vehicle in the Apollo program. The F-1 is still the most powerful single-chamber liquid-fueled rocket engine ever...
on the Saturn V
Saturn V
The Saturn V was an American human-rated expendable rocket used by NASA's Apollo and Skylab programs from 1967 until 1973. A multistage liquid-fueled launch vehicle, NASA launched 13 Saturn Vs from the Kennedy Space Center, Florida with no loss of crew or payload...
Rocket. 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
JP-7
JP-7 is a jet fuel developed by the U.S. Air Force for use in supersonic aircraft because of its high flash point and thermal stability. It is the fuel used in the Pratt & Whitney J58 engines, used in the Lockheed SR-71 Blackbird. The air compression of Mach 3+ cruising flight generates very high...
fuel has very low volatility and is difficult to ignite. Classical ignition plugs posed too high risk of a malfunction. It was used to start up each engine and to light the afterburner
AfterBurner
The AfterBurner is a lighting solution for the Game Boy Advance system that was created by Triton-Labs.Originally, portablemonopoly.net was a website created to petition Nintendo to put some kind of light in their Game Boy Advance system...
s.
The SpaceX
SpaceX
Space Exploration Technologies Corporation, or more popularly and informally known as SpaceX, is an American space transport company that operates out of Hawthorne, California...
Falcon 9
Falcon 9
Falcon 9 is a rocket-powered spaceflight launch system designed and manufactured by SpaceX. Both stages of its two-stage-to-orbit vehicle use liquid oxygen and rocket-grade kerosene propellants...
heavy-lift
Comparison of heavy lift launch systems
This page exposes the full list of orbital launch systems. For the short simple list of launchers families, see Comparison of orbital launchers families....
rocket
Rocket
A rocket is a missile, spacecraft, aircraft or other vehicle which obtains thrust from a rocket engine. In all rockets, the exhaust is formed entirely from propellants carried within the rocket before use. Rocket engines work by action and reaction...
uses a triethylaluminum-triethylborane mixture as a first-stage ignitor.
Industrially, triethylborane is used as an initiator
Initiator
An initiator can refer to:* A person that takes an initiative in making something happen.* Modulated neutron initiator, a neutron source used in some nuclear weapons...
in radical
Radical (chemistry)
Radicals are atoms, molecules, or ions with unpaired electrons on an open shell configuration. Free radicals may have positive, negative, or zero charge...
reactions, where it is effective even at low temperatures. As an initiator, it can replace some organotin
Organotin
Organotin compounds or stannanes are chemical compounds based on tin with hydrocarbon substituents. Organotin chemistry is part of the wider field of organometallic chemistry. The first organotin compound was diethyltin diiodide, discovered by Edward Frankland in 1849...
compounds. It reacts with metal enolates, yielding enoxytriethylborates with use in selective alkylation
Alkylation
Alkylation is the transfer of an alkyl group from one molecule to another. The alkyl group may be transferred as an alkyl carbocation, a free radical, a carbanion or a carbene . Alkylating agents are widely used in chemistry because the alkyl group is probably the most common group encountered in...
and aldol
Aldol
An aldol or aldol adduct is a beta-hydroxy ketone or aldehyde, and is the product of aldol addition ....
reactions. It is also used in reduction bond cleavage
Bond cleavage
Bond cleavage, or scission, is the splitting of chemical bonds.If the two electrons in a cleaved covalent bond are divided between the products, the process is known as homolytic fission and free redicals are generated by homolytic cleavage the process is known as homolytic fission or homolysis...
with lithium tri-tert-butoxyaluminohydride, in preparation of various boron
Boron
Boron is the chemical element with atomic number 5 and the chemical symbol B. Boron is a metalloid. Because boron is not produced by stellar nucleosynthesis, it is a low-abundance element in both the solar system and the Earth's crust. However, boron is concentrated on Earth by the...
compounds, deoxygenation
Deoxygenation
Deoxygenation is a chemical reaction involving the removal of molecular oxygen from a reaction mixture or solvent, or the removal of oxygen atoms from a molecule.Classic representatives of deoxygenation are:...
of primary and secondary alcohol
Alcohol
In chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....
s, rapid determination of -OH
Hydroxyl
A hydroxyl is a chemical group containing an oxygen atom covalently bonded with a hydrogen atom. In inorganic chemistry, the hydroxyl group is known as the hydroxide ion, and scientists and reference works generally use these different terms though they refer to the same chemical structure in...
groups in organic compounds, dehydration of salt and sugar hydrate
Hydrate
Hydrate is a term used in inorganic chemistry and organic chemistry to indicate that a substance contains water. The chemical state of the water varies widely between hydrates, some of which were so labeled before their chemical structure was understood....
s, determination of water content in crystalline hydrate compounds, in a variant of Reformatskii reaction
Reformatskii reaction
The Reformatsky reaction is an organic reaction which condenses aldehydes , 1, with α-halo esters, 2, using a metallic zinc to form β-hydroxy-esters, 3...
, and has a range of other uses in organoborane chemistry.
Triethylborane is used in vapor deposition
Vapor deposition
Vapor deposition can refer to:* Chemical vapor deposition* Physical vapor deposition...
techniques as a boron source. Examples are the plasma deposition of boron-containing hard carbon films, silicon nitride-boron nitride films, and for doping
Doping (semiconductor)
In semiconductor production, doping intentionally introduces impurities into an extremely pure semiconductor for the purpose of modulating its electrical properties. The impurities are dependent upon the type of semiconductor. Lightly and moderately doped semiconductors are referred to as extrinsic...
of diamond
Diamond
In mineralogy, diamond is an allotrope of carbon, where the carbon atoms are arranged in a variation of the face-centered cubic crystal structure called a diamond lattice. Diamond is less stable than graphite, but the conversion rate from diamond to graphite is negligible at ambient conditions...
film with boron. Other boron precursors used for such applications are e.g. trimethylborane
Trimethylborane
Trimethylborane is a toxic compound normally occurring as a gas that spontaneously catches fire in air. The formula is B3, which can also be expressed as Me3B, with Me representing methyl. Its melting point is -161.5 °C and boiling point is -20.2 °C.Vapour pressure is given by log P =...
, boron trifluoride
Boron trifluoride
Boron trifluoride is the chemical compound with the formula BF3. This pungent colourless toxic gas forms white fumes in moist air. It is a useful Lewis acid and a versatile building block for other boron compounds.-Structure and bonding:...
, diborane
Diborane
Diborane is the chemical compound consisting of boron and hydrogen with the formula B2H6. It is a colorless gas at room temperature with a repulsively sweet odor. Diborane mixes well with air, easily forming explosive mixtures. Diborane will ignite spontaneously in moist air at room temperature...
, and decaborane
Decaborane
Decaborane, also called decaborane, is the borane with the chemical formula B10H14. This white crystalline compound is one of the principal boron hydride clusters, both as a reference structure and as a precursor to other boron hydrides....
.
Sodium tetraethyl borate (NaTEB), a triethylboron derivative, is used as a powerful ethylation agent.