Sodium methoxide


Sodium methoxide is a chemical compound with the formula CH3ONa. This white solid, which is formed by the deprotonation of methanol, is a widely used reagent in industry and the laboratory. It is also a dangerously caustic base.

Preparation and structure

Sodium methoxide is prepared by treating methanol with sodium:
The reaction is so exothermic that ignition is possible. The resulting solution, which is colorless, is often used as a source of sodium methoxide, but the pure material can be isolated by evaporation followed by heating to remove residual methanol. The solid hydrolyzes in water to give methanol and sodium hydroxide. Indeed, samples of sodium methoxide are often contaminated with sodium hydroxide. The compound absorbs carbon dioxide from the air, thus diminishing the alkalinity of the base.
In the solid form, sodium methoxide is polymeric, with sheet-like arrays of Na+ centers, each bonded to four oxygen centers.
The structure, and hence the basicity, of sodium methoxide in solution depends on the solvent. It is a significantly stronger base in DMSO where it is more fully ionized and free of hydrogen bonding.

Applications

Organic synthesis

Sodium methoxide is a routinely used base in organic chemistry, applicable to the synthesis of numerous compounds ranging from pharmaceuticals to agrichemicals. As a base, it is employed in dehydrohalogenations and various condensations. It is also a nucleophile for the production of methyl ethers.

Industrial applications

Sodium methoxide is used as an initiator of anionic addition polymerization with ethylene oxide, forming a polyether with high molecular weight. Biodiesel is prepared from vegetable oils and animal fats, that is, fatty acid triglycerides, by transesterification with methanol to give fatty acid methyl esters. This transformation is catalyzed by sodium methoxide.

Safety

Sodium methoxide is highly caustic and reacts with water to give methanol, which is toxic and volatile.

NFPA 704

The ratings for this substance vary widely.