Chemistry:Triisobutylaluminium
 Monomeric form
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| Names | |
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| IUPAC name
Triisobutylaluminum
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| Other names
Aluminumtriisobutanide; TIBA
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| Identifiers | |
3D model (JSmol)
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| EC Number |
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PubChem CID
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| UNII | |
| UN number | 3394 3051 |
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| Properties | |
| 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 pictograms |  
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| GHS Signal word | Danger |
| H250, H260, H314 | |
| P210, P222, P223, P231+232, P260, P264, P280, P301+330+331, P302+334, P303+361+353, P304+340, P305+351+338, P310, P321, P335+334, P363, P370+378, P402+404, P405, P422, P501 | |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |
 verify (what is   ?)
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| Infobox references | |
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.[1]
Structure
Triisobutylaluminium exists in equilibrium with its dimer. The equilibrium constant, KD, is 3.810 at 20 °C.[2]
- 2 Al(CH2CH(CH3)2)3 [math]\ce{ <=>> }[/math] [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
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
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
Like most organoaluminium compounds, TiBA reacts violently with water and air.[3]
References
- ↑ 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.
- ↑ Cite error: Invalid
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Further reading
- Keisuke Suzuki, Tetsuya Nagasaws, Encyclopedia of Reagents for Organic Synthesis, Triisobutylaluminum, 2009
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