Aluminium isopropoxide is the

chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...

usually described with the formula Al(O-''i''-Pr)₃, where ''i''-Pr is the

isopropyl In organic chemistry, propyl is a three-carbon alkyl substituent with chemical formula for the linear form. This substituent form is obtained by removing one hydrogen atom attached to the terminal carbon of propane. A propyl substituent is ofte ...

group (–CH(CH₃)₂). This colourless solid is a useful

reagent In chemistry, a reagent ( ) or analytical reagent is a substance or compound added to a system to cause a chemical reaction, or test if one occurs. The terms ''reactant'' and ''reagent'' are often used interchangeably, but reactant specifies a ...

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 ...

Structure

A tetrameric structure of the crystalline material was verified by

NMR spectroscopy Nuclear magnetic resonance spectroscopy, most commonly known as NMR spectroscopy or magnetic resonance spectroscopy (MRS), is a spectroscopic technique to observe local magnetic fields around atomic nuclei. The sample is placed in a magnetic fiel ...

and

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

. The species is described by the formula Al μ-O-''i''-Pr)₂Al(O-''i''-Pr)₂sub>3. The unique central Al is octahedral, and three other Al centers adopt tetrahedral geometry. The idealised

point group symmetry In group theory, the symmetry group of a geometric object is the group of all transformations under which the object is invariant, endowed with the group operation of composition. Such a transformation is an invertible mapping of the ambient ...

is ''D₃''.

Preparation

This compound is commercially available. Industrially, it is prepared by the reaction between isopropyl alcohol and aluminium metal, or aluminium trichloride: :2 Al + 6 ''i''PrOH → 2 Al(O-''i''-Pr)₃ +3H₂ :AlCl₃ + 3 ''i''PrOH → Al(O-''i''-Pr)₃ + 3 HCl The procedure entails heating a mixture of aluminium,

isopropyl alcohol Isopropyl alcohol (IUPAC name propan-2-ol and also called isopropanol or 2-propanol) is a colorless, flammable organic compound with a pungent alcoholic odor. As an isopropyl group linked to a hydroxyl group (chemical formula ) it is the simple ...

, with a small amount of

mercuric chloride Mercury(II) chloride (or mercury bichloride, mercury dichloride), historically also known as sulema or corrosive sublimate, is the inorganic chemical compound of mercury and chlorine with the formula HgCl2. It is white crystalline solid and is a ...

. The process occurs via the formation of an

amalgam Amalgam most commonly refers to: * Amalgam (chemistry), mercury alloy * Amalgam (dentistry), material of silver tooth fillings ** Bonded amalgam, used in dentistry Amalgam may also refer to: * Amalgam Comics, a publisher * Amalgam Digital, an in ...

of the aluminium. A catalytic amount of

iodine Iodine is a chemical element with the symbol I and atomic number 53. The heaviest of the stable halogens, it exists as a semi-lustrous, non-metallic solid at standard conditions that melts to form a deep violet liquid at , and boils to a vi ...

is sometimes added to initiate the reaction. The industrial route does not use mercury.

Reactions

Aluminium isopropoxide is used in MPV reductions of

ketones In organic chemistry, a ketone is a functional group with the structure R–C(=O)–R', where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group –C(=O)– (which contains a carbon-oxygen double bon ...

and

aldehydes In organic chemistry, an aldehyde () is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred to as an aldehyde but can also be classified as a formyl group ...

and the

Oppenauer oxidation Oppenauer oxidation, named after , is a gentle method for selectively oxidizing secondary alcohols to ketones. The reaction is the opposite Meerwein–Ponndorf–Verley reduction. The alcohol is oxidized with aluminium isopropoxide in excess ace ...

of secondary alcohols. In these reactions, it is assumed that the tetrameric cluster disaggregates. It is used in the

Tishchenko reaction The Tishchenko reaction is an organic chemical reaction that involves disproportionation of an aldehyde in the presence of an alkoxide. The reaction is named after Russian organic chemist Vyacheslav Tishchenko, who discovered that aluminium alko ...

Being a basic

alkoxide In chemistry, an alkoxide is the conjugate base of an alcohol and therefore consists of an organic group bonded to a negatively charged oxygen atom. They are written as , where R is the organic substituent. Alkoxides are strong bases and, whe ...

, Al(O-i-Pr)₃ has been also investigated as a

catalyst Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...

for

ring opening polymerization In polymer chemistry, ring-opening polymerization (ROP) is a form of chain-growth polymerization, in which the terminus of a polymer chain attacks cyclic monomers to form a longer polymer (see figure). The reactive center can be radical, anion ...

cyclic ester Lactones are cyclic carboxylic esters, containing a 1-oxacycloalkan-2-one structure (), or analogues having unsaturation or heteroatoms replacing one or more carbon atoms of the ring. Lactones are formed by intramolecular esterification of the co ...

History

Aluminium isopropoxide was first reported in the master's thesis of the Russian organic chemist

Vyacheslav Tishchenko Vyacheslav Evgenievich Tishchenko (Вячеслав Евгеньевич Тищенко; 19 August 1861 – 25 February 1941) was a Russian chemist, best-known for the development of the Tishchenko reaction. Life and work Tishchenko was born in 1 ...

(Вячеслав Евгеньевич Тищенко, 1861–1941), which was reprinted in the ''Journal of the Russian Physico-Chemical Society'' (Журнал Русского Физико-Химического Общества) of 1899. This contribution included a detailed description of its synthesis, its peculiar physico-chemical behavior, and its catalytic activity in the

(catalytic transformation of aldehydes into esters). It was later found also to display catalytic activity as a reducing agent by Meerwein and Schmidt in the Meerwein–Ponndorf–Verley reduction ("MPV") in 1925. The reverse of the MPV reaction, oxidation of an alcohol to a ketone, is termed the

. The original Oppenauer oxidation employed aluminium butoxide in place of the isopropoxide.

Related compounds

Aluminium phenolate Aluminium phenolate is the metalloorganic compound with the formula l(OC6H5)3sub>n. It is a white solid. 27Al NMR studies suggest that aluminium phenolate exists in benzene solution as a mixture of dimer and trimer. The compound is can be pr ...

*Aluminium ''tert''-butoxide, which is a dimer ''t''-Bu-O)₂Al(μ-O-''t''-Bu)sub>2. It is prepared analogously to the isopropoxide.{{cite journal, first1 = Winston , last1 = Wayne , last2 = Adkins , first2 = Homer , author-link2 = Homer Burton Adkins , title = Aluminum ''tert''-Butoxide , journal = Organic Syntheses , year = 1941 , volume = 21 , pages = 8 , doi = 10.15227/orgsyn.021.0008

References

Alkoxides Aluminium compounds Isopropyl compounds