Abstract

Metal alkoxides are compounds in which a metal is attached to one or more alkyl groups by an oxygen atom. Alkoxides are derived from alcohols by the replacement of the hydroxyl hydrogen by metal. The metal alkoxides exhibit great differences in physical properties. Many metal alkoxides are soluble in the corresponding alcohols, but magnesium alkoxides are practically insoluble. The most outstanding property of the metal alkoxides is the ease of hydrolysis, used for sol–gel applications. Metal alkoxides catalyze the Tishchenko condensation of aldehydes, the transesterification of carboxylic esters, and other enolization and condensation reactions. Commercial alkoxides include alkali metal alkoxides (sodium methylate, sodium ethylate, sodium tert-butylate, sodium tert-amylate, potassium methylate, potassium ethylate, and potassium tert-butylate), alkaline-earth metal alkoxides (magnesium methylate, magnesium ethylate, and calcium methylate and ethylate), aluminum alkoxides (aluminum isopropylate and aluminum sec-butylate), transition-metal alkoxides (titanium alkoxides, zirconium alkoxides, and vanadium alkoxides), and antimony trialkoxides. Metal alkoxides are strongly caustic requiring the use of protective glasses and gloves. Metal alkoxides are mainly used as catalysts (in Ziegler-Natta polymerization, transesterifications, and condensations); in coatings for plastics, textiles, glass, and metals; in additives for adhesives and paints; for sol–gel applications; for synthesis of minerals capable of safely enclosing radioactive nuclear waste; and for the cross-linking or hardening of natural and synthetic materials. Alkali metal alkoxides find their principal use in organic synthesis where they act as strong bases.