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Aluminium isopropoxide

Aluminium isopropoxide
One enantiomorph of Al4(OiPr)12
Names
IUPAC name
Aluminium Isopropoxide
Other names
Triisopropoxyaluminium
Aluminium isopropanolate
Aluminium sec-propanolate
Aluminium triisopropoxide
2-Propanol aluminium salt
AIP
Identifiers
3D model (Jmol)
ChemSpider
ECHA InfoCard 100.008.265
RTECS number BD0975000
Properties
C9H21O3Al
Molar mass 204.25 g/mol
Appearance white solid
Density 1.035 g/cm³, solid
Melting point Sensitive to purity:
138–142 °C (99.99+%)
118 °C (98+%)
Boiling point @10 torr 135 °C (408 K)
Decomposes
Solubility in isopropanol Insoluble
Structure
monoclinic
Hazards
Main hazards Flammable (F)
R-phrases R11
S-phrases S8, S16
NFPA 704
Flammability code 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g., canola oil Health code 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g., chloroform Reactivity code 2: Undergoes violent chemical change at elevated temperatures and pressures, reacts violently with water, or may form explosive mixtures with water. E.g., phosphorus Special hazards (white): no codeNFPA 704 four-colored diamond
Flash point 16 °C (61 °F; 289 K)
Related compounds
Other cations
Titanium isopropoxide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
YesY  (what is YesYN ?)
Infobox references

Aluminium isopropoxide is the chemical compound usually described with the formula Al(O-i-Pr)3, where i-Pr is the isopropyl group (CH(CH3)2). This colourless solid is a useful reagent in organic synthesis. The structure of this compound is complex, possibly time-dependent, and may depend on solvent.

The structure of the metal alkoxides are often complex and aluminium isopropoxide is no exception. The complexity is also reflected in the disputed melting point for the material which could reflect the presence of trace impurities, such as water, slow oligomerisation ("aging") or both. For aluminium isopropoxide this phenomenon is mainly due to the trimer-tetramer transformation described in detail in the early works by Turova et al. The tetrameric structure of the solid crystalline material was verified by NMR spectroscopy and X-ray crystallography. The species is described by the formula Al[[(μ-O-i-Pr)2Al(O-i-Pr)2]]3. The unique central Al is octahedral surrounded by three bidentate "[[Al(O-i-Pr)4]]−" ligands, each featuring tetrahedral Al. The idealised point group symmetry is D3.

The tert-butoxide is a dimer with the formula Al2(μ-O-t-Bu)2(O-t-Bu)4 It is prepared analogously to the isopropoxide.

This compound is commercially available. Industrially, it is prepared by the reaction between isopropyl alcohol and aluminium metal, or aluminium trichloride:

Using aluminium metal, an older process uses a mercury catalyst (see below), whereas a more recent process does not.

In the laboratory, a widely accepted method for preparing aluminium isopropoxide was published in 1936 by Young, Hartung, and Crossley. Their procedure entails heating a mixture of 100 g of aluminium, 1200 mL of isopropyl alcohol, and 5 g of mercuric chloride at reflux. The process occurs via the formation of an amalgam of the aluminium. A catalytic amount of iodine is sometimes added to initiate the reaction, which can be quite vigorous. Young et al. achieved an 85–90% yield, after purification by distillation at 140–150 °C (5 mm Hg).


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