alkoxides

An alkoxide is a chemical species containing an oxygen atom bonded to an alkyl or aryl group and bearing a negative charge (RO−). In organic chemistry, RO− denotes the alkoxide ion, commonly used as a strong base and nucleophile. In inorganic and materials chemistry, the term also refers to metal alkoxides, M(OR)n, where a metal center is coordinated by alkoxide ligands. Metal alkoxides are widely used as precursors to metal oxides and as catalysts or building blocks in sol–gel chemistry.

Preparation and properties

Organic alkoxides are typically generated by deprotonating alcohols with strong bases such as sodium hydride, sodium metal, or by metathesis from alkoxide salts. They are highly basic and nucleophilic and are usually moisture sensitive. Metal alkoxides are prepared by reactions of metals or metal halides with alcohols or through transmetallation from alkoxide salts. Like organic alkoxides, they are often air- and moisture-sensitive and can hydrolyze or condense upon contact with water or CO2.

Reactivity and applications

Organic alkoxides serve as bases for deprotonations and as nucleophiles in substitutions such as the Williamson ether synthesis, enabling formation of ethers and various rearrangements. They are also used in transesterification and as catalysts in certain polymerization processes. Metal alkoxides function as versatile precursors for metal oxides (e.g., Al2O3, TiO2) via hydrolysis and polycondensation, forming networks used in coatings, ceramics, and catalysts. They also find roles in thin-film deposition and as catalysts in organic transformations, often under carefully controlled, moisture-free conditions.

Common examples

Sodium methoxide, NaOCH3; potassium tert-butoxide, KOtBu; aluminum isopropoxide, Al(OiPr)3; titanium isopropoxide, Ti(OiPr)4.