Diisobutylaluminium hydride
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| Names | |
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| IUPAC name
Diisobutylaluminum hydride
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| Other names
DIBAH; DIBAL; DiBAlH; DIBAL-H; DIBALH
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| Identifiers | |
1191-15-7  |
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| ChemSpider | 10430352 |
| Jmol 3D model | Interactive image |
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| Properties | |
| C16H38Al2 (dimer) | |
| Molar mass | 142.22 (monomer) |
| Appearance | colorless liquid |
| Density | 0.798 g/cm3 |
| Melting point | −80 °C (−112 °F; 193 K) |
| Boiling point | 116 to 118 °C (241 to 244 °F; 389 to 391 K) at 1 mmHg |
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| Vapor pressure | {{{value}}} |
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 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]
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
DIBALH, like most alkylaluminium compounds, reacts violently with air and water, potentially leading to fires.
References
External links
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