Diisobutylaluminium hydride (DIBALH, DIBAL, DIBAL-H or DIBAH) is a
reducing agent with the
formula
In science, a formula is a concise way of expressing information symbolically, as in a mathematical formula or a ''chemical formula''. The informal use of the term ''formula'' in science refers to the general construct of a relationship betwee ...
(''i''-Bu
2AlH)
2, where ''i''-Bu represents
isobutyl (-CH
2CH(CH
3)
2). This
organoaluminium compound is a reagent in organic synthesis.
[
]
Properties
Like most organoaluminum compounds, the compound's structure is most 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. Hydrides are small and, for aluminium derivatives, are highly basic
BASIC (Beginners' All-purpose Symbolic Instruction Code) is a family of general-purpose, high-level programming languages designed for ease of use. The original version was created by John G. Kemeny and Thomas E. Kurtz at Dartmouth College ...
, thus they bridge in preference to the alkyl groups.
DIBAL can be prepared by heating triisobutylaluminium (itself a dimer) to induce beta-hydride elimination:
:(''i''-Bu3Al)2 → (''i''-Bu2AlH)2 + 2 (CH3)2C=CH2
Although DIBAL 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
DIBAL is useful in organic synthesis
Organic synthesis is a special branch of chemical synthesis and is concerned with the intentional construction of organic compounds. Organic molecules are often more complex than inorganic compounds, and their synthesis has developed into one o ...
for a variety of reductions, including converting carboxylic acid
In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group () attached to an R-group. The general formula of a carboxylic acid is or , with R referring to the alkyl, alkenyl, aryl, or other group. Carboxylic ...
s, their derivatives, and nitrile
In organic chemistry, a nitrile is any organic compound that has a functional group. The prefix ''cyano-'' is used interchangeably with the term ''nitrile'' in industrial literature. Nitriles are found in many useful compounds, including met ...
s to aldehydes. DIBAL efficiently reduces α-β unsaturated esters to the corresponding allylic alcohol.acyl chloride
In organic chemistry, an acyl chloride (or acid chloride) is an organic compound with the functional group . Their formula is usually written , where R is a side chain. They are reactive derivatives of carboxylic acids (). A specific example o ...
s to primary alcohol
Alcohol most commonly refers to:
* Alcohol (chemistry), an organic compound in which a hydroxyl group is bound to a carbon atom
* Alcohol (drug), an intoxicant found in alcoholic drinks
Alcohol may also refer to:
Chemicals
* Ethanol, one of sev ...
s, and nitrile
In organic chemistry, a nitrile is any organic compound that has a functional group. The prefix ''cyano-'' is used interchangeably with the term ''nitrile'' in industrial literature. Nitriles are found in many useful compounds, including met ...
s to primary amines sing Fieser work-up procedure
Singing is the act of creating musical sounds with the voice. A person who sings is called a singer, artist or vocalist (in jazz and/or popular music). Singers perform music (arias, recitatives, songs, etc.) that can be sung with or without ...
DIBAL reacts slowly with electron-poor compounds, and more quickly with electron-rich compounds. Thus, it is an electrophilic
In chemistry, an electrophile is a chemical species that forms bonds with nucleophiles by accepting an electron pair. Because electrophiles accept electrons, they are Lewis acids. Most electrophiles are positively charged, have an atom that carri ...
reducing agent whereas LiAlH4 can be thought of as a nucleophilic reducing agent.
Although DIBAL reliably reduces nitriles to aldehydes, the reduction of esters to aldehydes is an infamously finicky reaction which looks useful on paper but often leads to mixtures of alcohol and aldehyde in practice. Nevertheless, it is possible to avoid these failures through careful control of the reaction conditions using continuous flow chemistry.
DIBALH was investigated originally as a cocatalyst for the polymerization of alkenes.
Safety
DIBAL, like most alkylaluminium compounds, reacts violently with air and water, potentially leading to explosion.
References
External links
*
*
*
{{Aluminium compounds
Organoaluminium compounds
Metal hydrides
Reducing agents