 | |
 | |
| Names | |
|---|---|
| IUPAC name Triethylalumane | |
| Identifiers | |
| |
3D model (JSmol) | |
| Abbreviations | TEA,[1] TEAl,[2] TEAL[3] |
| ChemSpider |
|
| ECHA InfoCard | 100.002.382 |
| EC Number |
|
| UNII | |
| UN number | 3051 |
| |
| Properties | |
| C12H30Al2 | |
| Molar mass | 228.335 g·mol−1 |
| Appearance | Colorless liquid |
| Density | 0.8324 g/mL at 25 °C |
| Melting point | −46 °C (−51 °F; 227 K) |
| Boiling point | 128 to 130 °C (262 to 266 °F; 401 to 403 K) at 50 mmHg |
| Reacts | |
| Solubility | Ether, hydrocarbons, THF |
| Hazards | |
| Occupational safety and health (OHS/OSH): | |
Main hazards | pyrophoric |
| GHS labelling: | |
  | |
| Danger | |
| H250,H260,H314 | |
| P210,P222,P223,P231+P232,P260,P264,P280,P301+P330+P331,P302+P334,P303+P361+P353,P304+P340,P305+P351+P338,P310,P321,P335+P334,P363,P370+P378,P402+P404,P405,P422,P501 | |
| NFPA 704 (fire diamond) | |
| Flash point | −18 °C (0 °F; 255 K) |
| Related compounds | |
Related compounds | Trimethylaluminium Triisobutylaluminium |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Triethylaluminium is one of the simplest examples of anorganoaluminium compound. Despite its name the compound has theformulaAl2(C2H5)6 (abbreviated as Al2Et6 or TEA). This colorless liquid ispyrophoric. It is an industrially important compound, closely related totrimethylaluminium.[4][5]
The structure and bonding in Al2R6 anddiborane 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.[6] 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 dimercracks into monomeric AlEt3.[7][8]
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, andethylene, summarized as follows:[4]
Because of this efficient synthesis, triethylaluminium is one of the most available organoaluminium compounds.
Triethylaluminium can also be generated fromethylaluminium sesquichloride (Al2Cl3Et3), which arises by treating aluminium powder withchloroethane. Reduction of ethylaluminium sesquichloride with analkali metal such as sodium gives triethylaluminium:[9]
The Al–C bonds of triethylaluminium arepolarized to such an extent that the carbon is easilyprotonated, releasing ethane:[10]
For this reaction, even weak acids can be employed such as terminalacetylenes and alcohols.
The linkage between the pair of aluminium centres is relatively weak and can be cleaved byLewis bases (L) to giveadducts with the formula AlEt3L:
Triethylaluminium is used industrially as an intermediate in the production offatty alcohols, which are converted todetergents. The first step involves theoligomerization of ethylene by theAufbau reaction, which gives a mixture of trialkylaluminium compounds (simplified here asoctyl groups):[4]
Subsequently, these trialkyl compounds are oxidized to aluminiumalkoxides, which are then hydrolysed:
A large amount of TEAL and related aluminium alkyls are used inZiegler-Natta catalysis. They serve to activate the transition metal catalyst both as a reducing agent and analkylating agent. TEAL also functions to scavenge water and oxygen.[11]
Triethylaluminium has niche uses as a precursor to other organoaluminium compounds, such asdiethylaluminium cyanide:[12]
Triethylaluminium ignites on contact with air and will ignite and/or decompose on contact with water, and with any other oxidizer[13]—it is one of the few substances sufficiently pyrophoric to ignite on contact with cryogenicliquid oxygen. Theenthalpy of combustion, ΔcH°, is–5105.70 ± 2.90 kJ/mol[14] (–22.36 kJ/g). Its easy ignition makes it particularly desirable as arocket engineignitor. TheSpaceXFalcon 9rocket uses a triethylaluminium-triethylborane mixture as a first-stage ignitor.[1]
Triethylaluminiumthickened withpolyisobutylene is used as anincendiary weapon, as a pyrophoric alternative tonapalm; e.g., in the M74 clip holding four rockets for theM202A1 launchers.[15] In this application it is known as TPA, forthickened pyrotechnic agent orthickened 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.[16] 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.
Triethylaluminum (TEAl) is a pyrophoric liquid...
