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Triisobutylaluminium

Triisobutylaluminium

Monomeric form
Names
IUPAC name
Triisobutylaluminum
Other names
Aluminumtriisobutanide; TIBA
Identifiers
3D model (JSmol)
ECHA InfoCard 100.002.643 Edit this at Wikidata
EC Number
  • 202-906-3
UNII
UN number 3394 3051
  • InChI=1S/3C4H9.Al/c3*1-4(2)3;/h3*4H,1H2,2-3H3;
    Key: MCULRUJILOGHCJ-UHFFFAOYSA-N
  • CC(C)C[Al](CC(C)C)CC(C)C
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:
GHS02: FlammableGHS05: Corrosive
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

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

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.[1]

References

  1. ^ a b Sigma-Aldrich. "Triisobutylaluminum". MilliporeSigma. Merck Group. Retrieved 2021-03-15.
  2. ^ 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
  3. ^ 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

  • Keisuke Suzuki, Tetsuya Nagasaws, Encyclopedia of Reagents for Organic Synthesis, Triisobutylaluminum, 2009
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