Triisobutylaluminium
 Monomeric form
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| Names | |
|---|---|
| IUPAC name
Triisobutylaluminum
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| Other names
Aluminumtriisobutanide; TIBA
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| Identifiers | |
3D model (JSmol)
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| ECHA InfoCard | 100.002.643 |
| EC Number |
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PubChem CID
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| UNII | |
| UN number | 3394 3051 |
CompTox Dashboard (EPA)
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| Properties[1] | |
| C12H27Al | |
| Molar mass | 198.330 g·mol−1 |
| Appearance | Colorless liquid |
| Density | 0.786 g/mL at 25 °C |
| Melting point | 4 to 6 °C (39 to 43 °F; 277 to 279 K) |
| Boiling point | 86 °C (13 hPa) |
| Hazards | |
| GHS labelling: | |
 
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| 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 | |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Triisobutylaluminium (TiBA) is an organoaluminium compound with the formula Al(CH2CH(CH3)2)3. This colorless pyrophoric liquid is mainly used to make linear primary alcohols and α-olefins.[2]
Structure
[edit]Triisobutylaluminium exists in equilibrium with its dimer. The equilibrium constant, KD, is 3.810 at 20 °C.[3]
- 2 Al(CH2CH(CH3)2)3 [Al(CH2CH(CH3)2)3]2
In the dimer, the bridging carbon-aluminium bond is elongated and exhibits evidence of restricted rotation. For the sake of simplicity, TiBA is written as the monomer in this article.
Synthesis
[edit]Trialkylaluminium compounds are available industrially through the reactions of aluminium powder, hydrogen gas, and the desired alkenes. The synthesis of TiBA requires two steps; the first step produces diisobutylaluminium hydride (written as a monomer):
- 4 CH2=C(CH3)2 + 2 Al + 3 H2 → 2 HAl(CH2CH(CH3)2)2
In the second step isobutylene adds to the diisobutylaluminium to give TiBA:
- CH2=C(CH3)2 + HAl(CH2CH(CH3)2)2 → Al(CH2CH(CH3)2)3
Reactions
[edit]α-olefins are readily eliminated from β-branched trialkylaluminium compounds. Trialkylaluminium compounds are used in the industrial production of polymers. In the most common of these compounds, TIBA, a substantial level of Al – H bonds are present at equilibrium. The greater stability of unbranched trialkylaluminium compounds relative to branched trialkylaluminium compounds in TIBA forms the basis for a general synthesis of triethyl- and higher linear trialkylaluminium materials from triisobutylaluminium.
- Al(CH2CH(CH3)2)3 + 3 RCH=CH2 → Al(CH2CH2R)3 + 3 CH2=C(CH3)2
Safety
[edit]Like most organoaluminium compounds, TiBA reacts violently with water and air.[1]
References
[edit]- ^ a b Sigma-Aldrich. "Triisobutylaluminum". MilliporeSigma. Merck Group. Retrieved 2021-03-15.
- ^ Michael J. Krause, Frank Orlandi, Alfred T. Saurage, Joseph R. Zietz Jr. "Aluminum Compounds, Organic" in Ullmann's Encyclopedia of Industrial Chemistry 2002, Wiley-VCH, Weinheim. doi:10.1002/14356007.a01_543
- ^ Smith, Martin B. (1970). "The Monomer-Dimer Equilibria of Liquid Ammonium Alkyls II Triisobutylaluminum". Journal of Organometallic Chemistry. 22 (2): 273–281. doi:10.1016/S0022-328X(00)86043-X.
Further reading
[edit]- Keisuke Suzuki, Tetsuya Nagasaws, Encyclopedia of Reagents for Organic Synthesis, Triisobutylaluminum, 2009