Aluminium isopropoxide
[CAS 555-31-7]

Identification

• Classification: Organic raw materials >> Organometallic compound >> Organic aluminum
• Name: Aluminium isopropoxide
• Synonyms: 2-Propanol aluminum salt; AIP; Aluminium isopropylate
• Molecular Formula: C₉H₂₁AlO₃
• Molecular Weight: 204.24
• CAS Registry Number: 555-31-7
• EC Number: 209-090-8
• SMILES: CC(C)[O-].CC(C)[O-].CC(C)[O-].[Al+3]

Properties

• Density: 1.035 g/mL (Expl.)
• Melting point: 128 - 133 °C (Expl.)
• Boiling point: 315.3 °C (Expl.)
• Flash point: 16 °C (Expl.)
• Solubility: Soluble in alcohol, benzene, and toluene. Decomposes in water (Expl.)
• Refraction index: 1.035 (Expl.)

Safety Data

• Hazard Symbols: GHS02 DangerGHS02
• Risk Statements: H228
• Safety Statements: P210-P240-P241-P280-P370+P378

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Flammable solids	Flam. Sol.	1	H228
Serious eye damage	Eye Dam.	1	H318
Skin corrosion	Skin Corr.	1C	H314
Specific target organ toxicity - single exposure	STOT SE	3	H336
Eye irritation	Eye Irrit.	2	H319

• Transport Information: UN 3181

chemBlink Chemical Story

Aluminium isopropoxide, CAS 555-31-7, is one of the most familiar aluminium alkoxides, commonly written Al(O-i-Pr)3. PubChem records the idealized formula C9H21AlO3 and describes it as a useful reagent in organic synthesis. In the condensed state aluminium alkoxides can form associated structures, but the simple formula conveniently expresses the three isopropoxide ligands attached to aluminium.

Its classic organic reaction is the Meerwein-Ponndorf-Verley reduction. In this process an aluminium alkoxide coordinates a ketone or aldehyde and enables hydride transfer from a secondary alcohol, commonly isopropanol, through a six-membered transition-state arrangement. The carbonyl compound is reduced to an alcohol while the donor alcohol is oxidized to a ketone. The reverse transformation, oxidation of an alcohol by a ketone such as acetone, is known as the Oppenauer oxidation. Together these reactions became classic examples of chemoselective transfer-hydrogen chemistry.

Aluminium isopropoxide is also a major precursor in sol-gel and materials chemistry. Its Al-O-C bonds hydrolyze in water, and subsequent condensation builds Al-O-Al networks. By controlling water, solvent, temperature and additives, researchers use this chemistry to prepare alumina, mixed oxides, coatings and catalyst supports. PubChem records industrial use as a chemical intermediate and extensive patent use as an aluminium source.

Moisture sensitivity is therefore both a feature and a handling issue. Water destroys the original alkoxide but that same hydrolysis is exactly what materials chemists exploit to build oxide structures. In organic synthesis, by contrast, unwanted water can interfere with controlled reagent behavior.

Aluminium isopropoxide is unusual in how comfortably it belongs to two different chemical traditions. Organic chemists know it for carbonyl transfer hydrogenation; materials chemists know it as a molecular route to aluminium oxide. In both cases, the useful chemistry comes from the reactive aluminium-oxygen bonds and the exchangeability of the isopropoxide ligands.

References:
1. PubChem, Aluminum isopropoxide, CID 11143, CAS 555-31-7.
2. Wilds AL. Reduction with aluminum alkoxides. Org React. 1944;2:178-223.
3. Brinker CJ, Scherer GW. Sol-Gel Science. Academic Press, 1990.

Read more stories