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EspañolDIISOBUTYLALUMINIUM HYDRIDE
(Redirected from DIBAL)
'Diisobutylaluminium hydride', DIBAL, DIBAL-H or DIBAH, 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]
Like most organoaluminum compounds, the compound’s structure is more than that suggested by its empirical formula. It is dimeric, consisting of a pair of tetrahedral aluminium centers sharing bridging hydride ligands. Hydrides are small and, for aluminium derivatives, are highly basic, thus they bridge in preference to the alkyl groups.
DIBAH can be prepared by heating triisobutylaluminium (itself a dimer) to induce beta-hydride elimination:[2]
:(''i''-Bu3Al)2 → (''i''-Bu2AlH)2 + 2 (CH3)2C=CH2
Although DIBAH can be purchased commercially as a colorless liquid, it is more commonly purchased and dispensed as a solution in organic solvents such as toluene.
DIBAH is useful in organic synthesis for a variety of reductions, including converting esters and nitriles to aldehydes.[3] By contrast, LiAlH4 reduces esters and acyl chlorides to primary alcohols, and NaBH4 fails to reduce most esters. DIBAH 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.
DIBAH, like most alkylaluminium compounds, reacts violently with air and water, potentially leading to fires.
1. Metallorganische Verbindungen, XXVII Aluminiumtrialkyle und Dialkyl-Aluminiumhydride Aus Aluminiumisobutyl-Verbindungen, K. Ziegler, H. Martin and F. Krupp, , , Justus Liebigs Annalen der Chemie, 1960
2. Eisch, J. J. Organometallic Syntheses Volume 2, Academic Press: New York, 1981. ISBN 0-12-234950-4.
3. Galatsis, P. “Diisobutylaluminum Hydride” in Encyclopedia of Reagents for Organic Synthesis John Wiley & Sons: New York, 2001.
★ Example use
★ Overview of reduction
'Diisobutylaluminium hydride', DIBAL, DIBAL-H or DIBAH, 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 |
| Use in organic synthesis |
| Safety |
| References |
| External links |
Properties
Like most organoaluminum compounds, the compound’s structure is more than that suggested by its empirical formula. It is dimeric, consisting of a pair of tetrahedral aluminium centers sharing bridging hydride ligands. Hydrides are small and, for aluminium derivatives, are highly basic, thus they bridge in preference to the alkyl groups.
DIBAH can be prepared by heating triisobutylaluminium (itself a dimer) to induce beta-hydride elimination:[2]
:(''i''-Bu3Al)2 → (''i''-Bu2AlH)2 + 2 (CH3)2C=CH2
Although DIBAH can be purchased commercially as a colorless liquid, it is more commonly purchased and dispensed as a solution in organic solvents such as toluene.
Use in organic synthesis
DIBAH is useful in organic synthesis for a variety of reductions, including converting esters and nitriles to aldehydes.[3] By contrast, LiAlH4 reduces esters and acyl chlorides to primary alcohols, and NaBH4 fails to reduce most esters. DIBAH 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
1. Metallorganische Verbindungen, XXVII Aluminiumtrialkyle und Dialkyl-Aluminiumhydride Aus Aluminiumisobutyl-Verbindungen, K. Ziegler, H. Martin and F. Krupp, , , Justus Liebigs Annalen der Chemie, 1960
2. Eisch, J. J. Organometallic Syntheses Volume 2, Academic Press: New York, 1981. ISBN 0-12-234950-4.
3. Galatsis, P. “Diisobutylaluminum Hydride” in Encyclopedia of Reagents for Organic Synthesis John Wiley & Sons: New York, 2001.
External links
★ Example use
★ Overview of reduction
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