Alkoxide

An alkoxide is an anion RO− derived from an alcohol ROH by deprotonation. The R group is typically alkyl; common examples include methoxide (CH3O−), ethoxide (C2H5O−), and tert-butoxide ( t−BuO−), usually paired with a counter‑ion such as Na+, K+, or Li+. Alkoxides are both strong bases and good nucleophiles; their conjugate acids are alcohols, so RO− strength correlates with the pKa of the corresponding alcohol (roughly 16–19). Many alkoxides are moisture and air sensitive and react with CO2 to form carbonates and alcohols.

Preparation and sources: Alkoxides are typically generated by deprotonating an alcohol with a strong base (for example NaH, Na, or NaNH2) or by metathesis of metal salts with alkoxide sources. In industry, sodium methoxide and sodium ethoxide are prepared by treating the corresponding alcohols with reactive metals or bases.

Reactions and uses: Alkoxides serve as bases in deprotonations and as nucleophiles in substitutions. In organic synthesis, they participate in the Williamson ether synthesis to form new ethers (RO− + R′X → ROR′). They react with acyl chlorides and anhydrides to give esters. In solution, RO− can act as ligands in coordination chemistry. Metal alkoxides such as Ti(OiPr)4 are important precursors in sol–gel processes for making ceramics and glasses.

Examples and handling: Common members include sodium methoxide, sodium ethoxide, and potassium tert-butoxide. They are caustic and readily hydrolyze in moisture or on exposure to air; storage and use typically require inert, dry conditions.