phenolates

Phenolates, or phenoxides, are the conjugate bases of phenols. They have the general formula Ar–O− M+, where Ar is an aryl group (typically phenyl) and M+ is a counterion such as Na+, K+, or other alkali or alkaline-earth cations. They are formed by deprotonation of phenols with bases such as sodium hydroxide, sodium hydride, or potassium carbonate. The negative charge is delocalized over the aromatic ring by resonance, stabilizing the anion and giving phenols their relatively acidic character (pKa around 9–11 in water). Substituents on the ring modulate both acidity and nucleophilicity.

Phenolates are usually isolated as salts and are typically colorless solids or viscous liquids that dissolve in polar solvents. They act as strong nucleophiles and bases. In organic synthesis, the oxygen atom is the primary nucleophilic site; reaction with alkyl halides produces aryl ethers via the Williamson ether synthesis. They also react with acyl chlorides to give esters. Under certain conditions, there can be competing C-alkylation or other pathways, but O-alkylation is the common outcome.

Applications and considerations: Sodium phenoxide and related salts serve as versatile reagents for forming aryl ethers and phenyl esters, and they function as bases in various transformation sequences. Safety and handling are important, as phenolates are caustic and can irritate skin and eyes; appropriate protective equipment and procedures are advised when working with these reagents.