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Suggest pagesDiisobutylaluminium hydride
| Diisobutylaluminium hydride | |
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Diisobutylaluminum hydride |
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Other names
DIBAH; DIBAL; DiBAlH; DIBAL-H; DIBALH |
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| Identifiers | |
| CAS number | 1191-15-7  |
| ChemSpider | 10430352 |
| Jmol-3D images | Image 1 |
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| Properties | |
| Molecular formula | C16H38Al2 (dimer) |
| Molar mass | 142.22 (monomer) |
| Appearance | colorless liquid |
| Density | 0.798 g/cm3 |
| Melting point |
–80 °C |
| Boiling point |
116–118 °C/1 mmHg |
| Solubility in water | hydrocarbon solvents |
| Hazards | |
| Main hazards | ignites in air |
 (verify) (what is:  / ?)Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
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| Infobox references | |
Diisobutylaluminium hydride (DIBALH, DIBAL, DIBAL-H or DIBAH, DYE-bal) is a reducing agent with the formula (i-Bu2AlH)2, where i-Bu represents isobutyl (-CH2CH(CH3)2). This organoaluminium compound was investigated originally as a co-catalyst for the polymerization of alkenes.1
Contents |
Properties
Like most organoaluminum compounds, the compound’s structure is probably more than that suggested by its empirical formula. A variety of techniques, not including X-ray crystallography, suggest that the compound exists as a dimer and a trimer, consisting of tetrahedral aluminium centers sharing bridging hydride ligands.2 Hydrides are small and, for aluminium derivatives, are highly basic, thus they bridge in preference to the alkyl groups.
DIBALH can be prepared by heating triisobutylaluminium (itself a dimer) to induce beta-hydride elimination:3
- (i-Bu3Al)2 → (i-Bu2AlH)2 + 2 (CH3)2C=CH2
Although DIBALH can be purchased commercially as a colorless liquid, it is more commonly purchased and dispensed as a solution in an organic solvent such as toluene or hexane.
Use in organic synthesis
DIBALH is useful in organic synthesis for a variety of reductions, including converting esters and nitriles to aldehydes. DIBALH efficiently reduces α-β unsaturated esters to the corresponding allylic alcohol.4 By contrast, LiAlH4 reduces esters and acyl chlorides to primary alcohols, and nitriles to primary amines [use Feiser work-up procedure]. DIBALH reacts slowly with electron-poor compounds, and more quickly with electron-rich compounds. Thus, it is an electrophilic reducing agent whereas LiAlH4 can be thought of as a nucleophilic reducing agent.
Safety
DIBAH, like most alkylaluminium compounds, reacts violently with air and water, potentially leading to fires.
References
- ^ Ziegler, K.; Martin, H.; Krupp, F. (1960). "Metallorganische Verbindungen, XXVII Aluminiumtrialkyle und Dialkyl-Aluminiumhydride aus Aluminiumisobutyl-Verbindungen". Justus Liebigs Annalen der Chemie 629 (1): 14–19. doi:10.1002/jlac.19606290103.
- ^ Self, M. F.; Pennington, W. T.; Robinson, G. H. (1990). "Reaction of Diisobutylaluminum Hydride with a Macrocyclic Tetradentate Secondary Amine. Synthesis and Molecular Structure of [Al(iso-Bu)]2[C10H20N4[Al(iso-Bu)32: Evidence of an Unusual Disproportionation of (iso-Bu)2AlH". Inorganica Chimica Acta 175 (2): 151–153. doi:10.1016/S0020-1693(00)84819-7.
- ^ Eisch, J. J. (1981). Organometallic Syntheses 2. New York: Academic Press. ISBN 0-12-234950-4.
- ^ Galatsis, P. (2001). "Diisobutylaluminum Hydride". Encyclopedia of Reagents for Organic Synthesis. New York: John Wiley & Sons. doi:10.1002/047084289X.rd245.
External links
- Stockman, R. (2001). "Dibal reduction of an amino acid derived methyl ester; Garner's Aldehyde". ChemSpider Synthetic Pages. doi:10.1039/SP161. SyntheticPage 161.
- "Oxidation And Reduction Reactions in Organic Chemistry". University of Southern Maine, Department of Chemistry.
- "Diisobutyl Aluminum hydride (DIBAL-H) and Other Isobutyl Aluminum Alkyls (DIBAL-BOT, TIBAL) as Specialty Organic Synthesis Reagents". Akzo-Nobel.
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