Diisobutylaluminium hydride (DIBALH, DIBAL, DIBAL-H or DIBAH) is a

reducing agent In chemistry, a reducing agent (also known as a reductant, reducer, or electron donor) is a chemical species that "donates" an electron to an (called the , , , or ). Examples of substances that are common reducing agents include hydrogen, carbon ...

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 betwe ...

(''i''-Bu₂AlH)₂, where ''i''-Bu represents

isobutyl In organic chemistry, butyl is a four-carbon alkyl radical or substituent group with general chemical formula , derived from either of the two isomers (''n''-butane and isobutane) of butane. The isomer ''n''-butane can connect in two ways, giv ...

(-CH₂CH(CH₃)₂). This

organoaluminium compound Organoaluminium chemistry is the study of compounds containing bonds between carbon and aluminium. It is one of the major themes within organometallic chemistry. Illustrative organoaluminium compounds are the dimer trimethylaluminium, the monomer ...

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 In chemistry, the empirical formula of a chemical compound is the simplest whole number ratio of atoms present in a compound. A simple example of this concept is that the empirical formula of sulfur monoxide, or SO, is simply SO, as is the empir ...

. A variety of techniques, not including

X-ray crystallography X-ray crystallography is the experimental science of determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to Diffraction, diffract in specific directions. By measuring th ...

, suggest that the compound exists as a dimer and a trimer, consisting of tetrahedral aluminium centers sharing bridging

hydride In chemistry, a hydride is formally the anion of hydrogen (H−), a hydrogen ion with two electrons. In modern usage, this is typically only used for ionic bonds, but it is sometimes (and has been more frequently in the past) applied to all che ...

ligand In coordination chemistry, a ligand is an ion or molecule with a functional group that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's el ...

s. Hydrides are small and, for aluminium derivatives, are highly

basic Basic or BASIC may refer to: Science and technology * BASIC, a computer programming language * Basic (chemistry), having the properties of a base * Basic access authentication, in HTTP Entertainment * Basic (film), ''Basic'' (film), a 2003 film ...

, thus they bridge in preference to the

alkyl In organic chemistry, an alkyl group is an alkane missing one hydrogen. The term ''alkyl'' is intentionally unspecific to include many possible substitutions. An acyclic alkyl has the general formula of . A cycloalkyl group is derived from a cy ...

groups. DIBAL can be prepared by heating

triisobutylaluminium 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 alcohol Alcohol may refer to: Common uses * Alcohol (chemistry), a class of ...

(itself a dimer) to induce β-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 Toluene (), also known as toluol (), is a substituted aromatic hydrocarbon with the chemical formula , often abbreviated as , where Ph stands for the phenyl group. It is a colorless, water Water is an inorganic compound with the c ...

hexane Hexane () or ''n''-hexane is an organic compound, a straight-chain alkane with six carbon atoms and the molecular formula C6H14. Hexane is a colorless liquid, odorless when pure, and with a boiling point of approximately . It is widely used as ...

Use in organic synthesis

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 carr ...

reducing agent whereas LiAlH₄ can be thought of as a

nucleophilic In chemistry, a nucleophile is a chemical species that forms bonds by donating an electron pair. All molecules and ions with a free pair of electrons or at least one pi bond can act as nucleophiles. Because nucleophiles donate electrons, they a ...

reducing agent. DIBAL is useful in

organic synthesis Organic synthesis is a branch of chemical synthesis concerned with the construction of organic compounds. Organic compounds are molecules consisting of combinations of covalently-linked hydrogen, carbon, oxygen, and nitrogen atoms. Within the gen ...

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 Substituent, R-group. The general formula of a carboxylic acid is often written as or , sometimes as with R referring to an organyl ...

s, their derivatives, and

nitrile In organic chemistry, a nitrile is any organic compound that has a functional group. The name of the compound is composed of a base, which includes the carbon of the , suffixed with "nitrile", so for example is called " propionitrile" (or pr ...

s to

aldehyde In organic chemistry, an aldehyde () (lat. ''al''cohol ''dehyd''rogenatum, dehydrogenated alcohol) is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred ...

s. DIBAL efficiently reduces α-β unsaturated esters to the corresponding allylic alcohol. By contrast, LiAlH₄ reduces esters and

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

alcohols In chemistry, an alcohol (), is a type of organic compound that carries at least one hydroxyl () functional group bound to a Saturated and unsaturated compounds, saturated carbon atom. Alcohols range from the simple, like methanol and ethanol ...

, and

s to primary

amine In chemistry, amines (, ) are organic compounds that contain carbon-nitrogen bonds. Amines are formed when one or more hydrogen atoms in ammonia are replaced by alkyl or aryl groups. The nitrogen atom in an amine possesses a lone pair of elec ...

s sing Fieser work-up procedure Similarly, DIBAL reduces

lactone Lactones are cyclic carboxylic esters. They are derived from the corresponding hydroxycarboxylic acids by esterification. They can be saturated or unsaturated. Lactones are formed by lactonization, the intramolecular esterification of the corresp ...

s to

hemiacetal In organic chemistry, a hemiacetal is a functional group the general formula , where is a hydrogen atom or an organic substituent. They generally result from the nucleophilic Addition reaction, addition of an Alcohol (chemistry), alcohol (a compo ...

s (the equivalent of an aldehyde). Although DIBAL reliably reduces nitriles to aldehydes, the reduction of esters to aldehydes is infamous for often producing large quantities of alcohols. Nevertheless, it is possible to avoid these unwanted byproducts through careful control of the reaction conditions using continuous

flow chemistry In flow chemistry, also called reactor engineering, a chemical reaction is run in a continuously flowing stream rather than in batch production. In other words, pumps move fluid into a reactor, and where tubes join one another, the fluids contac ...

. DIBALH was investigated originally as a

cocatalyst Catalysis () is the increase in rate of a chemical reaction due to an added substance known as a catalyst (). Catalysts are not consumed by the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recycles quick ...

for the

polymerization In polymer chemistry, polymerization (American English), or polymerisation (British English), is a process of reacting monomer molecules together in a chemical reaction to form polymer chains or three-dimensional networks. There are many fo ...

alkene In organic chemistry, an alkene, or olefin, is a hydrocarbon containing a carbon–carbon double bond. The double bond may be internal or at the terminal position. Terminal alkenes are also known as Alpha-olefin, α-olefins. The Internationa ...

Safety

DIBAL, like most alkylaluminium compounds, reacts violently with air and water, potentially leading to explosion.

References

External links

* * * {{Aluminium compounds Isobutyl compounds Metal hydrides Organoaluminium compounds Reducing agents