chemistry

Triethylaluminium

Triethylaluminium is a chemistry topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Triethylaluminium rather than just read about it. In short: Triethylaluminium (generally abbreviated as TEA) is one of the simplest examples of an organoaluminium compound. Despite its name, the compound has the formula Al2(C2H5)6, which equates to the dimer of the expected species.

Key takeaways

Triethylaluminium belongs to chemistry; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Triethylaluminium to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Triethylaluminium from memory before moving on to harder problems.

Reference excerpt

Triethylaluminium (generally abbreviated as TEA) is one of the simplest examples of an organoaluminium compound. Despite its name, the compound has the formula Al2(C2H5)6, which equates to the dimer of the expected species. This kind of oligomerization is common in sterically unhindered organometallics. It is an exceedingly pyrophoric material that exists as a colourless liquid over a wide range of temperatures. It is an industrially important compound, closely related to trimethylaluminium.

Structure and bonding The structure and bonding in Al2R6 and diborane are analogous (R = alkyl). Referring to Al2Me6, the Al-C(terminal) and Al-C(bridging) distances are 1.97 and 2.14 Å, respectively. The Al center is tetrahedral. The carbon atoms of the bridging ethyl groups are each surrounded by five neighbors: carbon, two hydrogen atoms and two aluminium atoms. The ethyl groups interchange readily intramolecularly. At higher temperatures, the dimer cracks into monomeric AlEt3.

Synthesis and reactions Triethylaluminium can be formed via several routes. The discovery of an efficient route was a significant technological achievement. The multistep process uses aluminium, hydrogen gas, and ethylene, summarized as follows:

2 Al + 3 H2 + 6 C2H4 → Al2Et6 Because of this efficient synthesis, triethylaluminium is one of the most available organoaluminium compounds. Triethylaluminium can also be generated from ethylaluminium sesquichloride (Al2Cl3Et3), which arises by treating aluminium powder with chloroethane. Reduction of ethylaluminium sesquichloride with an alkali metal such as sodium gives triethylaluminium:

6 Al2Cl3Et3 + 18 Na → 3 Al2Et6 + 6 Al + 18 NaCl

Reactivity The Al–C bonds of triethylaluminium are polarized to such an extent that the carbon is easily protonated, releasing ethane:

Al2Et6 + 6 HX → 2 AlX3 + 6 EtH For this reaction, even weak acids can be employed such as terminal acetylenes and alcohols. The linkage between the pair of aluminium centres is relatively weak and can be cleaved by Lewis bases (L) to give adducts with the formula AlEt3L:

Al2Et6 + 2 L → 2 LAlEt3

Applications

Precursors to fatty alcohols Triethylaluminium is used industrially as an intermediate in the production of fatty alcohols, which are converted to detergents. The first step involves the oligomerization of ethylene by the Aufbau reaction, which gives a mixture of trialkylaluminium compounds (simplified here as octyl groups):

Al2(C2H5)6 + 18 C2H4 → Al2(C8H17)6 Subsequently, these trialkyl compounds are oxidized to aluminium alkoxides, which are then hydrolysed:

Al2(C8H17)6 + 3 O2 → Al2(OC8H17)6 Al2(OC8H17)6 + 6 H2O → 6 C8H17OH + 2 Al(OH)3

Co-catalysts in olefin polymerization A large amount of TEAL and related aluminium alkyls are used in Ziegler-Natta catalysis. They serve to activate the transition metal catalyst both as a reducing agent and an alkylating agent. TEAL also functions to scavenge water and oxygen.

Reagent in organic and organometallic chemistry Triethylaluminium has niche uses as a precursor to other organoaluminium compounds, such as diethylaluminium cyanide:

1 2 Al 2 Et 6 + HCN ⟶ 1 n [ Et 2 AlCN ] n + C 2 H 6 {\displaystyle {\ce {{1/2Al2Et6}+ HCN ->}}\ {\tfrac {1}{n}}{\ce {[Et2AlCN]}}_{n}+{\ce {C2H6}}}

Pyrophoric agent Triethylaluminium ignites on contact with air and will ignite and/or decompose on contact with water, and with any other oxidizer—it is one of the few substances sufficiently pyrophoric to ignite on contact with cryogenic liquid oxygen. The enthalpy of combustion, ΔcH°, is –5105.70 ± 2.90 kJ/mol (–22.36 kJ/g). Its easy ignition makes it particularly desirable as a rocket engine ignitor. The SpaceX Falcon 9 rocket uses a triethylaluminium-triethylborane mixture as a first-stage ignitor. Triethylaluminium thickened with polyisobutylene is used as an incendiary weapon, as a pyrophoric alternative to napalm; e.g., in the M74 clip holding four rockets for the M202A1 launchers. In this application it is known as TPA, for thickened pyrotechnic agent or thickened pyrophoric agent. The usual amount of the thickener is 6%. The amount of thickener can be decreased to 1% if other diluents are added. For example, n-hexane, can be used with increased safety by rendering the compound non-pyrophoric until the diluent evaporates, at which point a combined fireball results from both the triethylaluminium and the hexane vapors. The M202 was withdrawn from service in the mid-1980s owing to safety, transport, and storage issues. Some saw limited use in the Afghanistan War against caves and fortified compounds.

See also Triethylborane, used as an ignitor in the Pratt & Whitney J58 turbojet/ramjet engines. Trimethylaluminium

References

Illustrations

Worked examples

Example 1 — a first encounter with Triethylaluminium

Start with the simplest possible case. Write down what Triethylaluminium claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Triethylaluminium before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Triethylaluminium ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Triethylaluminium

In research: Triethylaluminium appears in chemistry research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Triethylaluminium in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Triethylaluminium is common in secondary-school and first-year university syllabi. It links to neighbouring topics Dimers (chemistry), Ethyl compounds, Four-membered rings, so understanding it makes those chapters shorter.
In everyday life: Look for Triethylaluminium outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Triethylaluminium in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Triethylaluminium means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Triethylaluminium out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Triethylaluminium in simple terms?

Why does Triethylaluminium matter?

Because it connects several chemistry ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Triethylaluminium?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Triethylaluminium.