KOtBu

Potassium tert-butoxide (KOtBu) is a strong, bulky organic base used widely in organic synthesis. Its formula is C4H9KO, and its systematic IUPAC name is potassium 2-methylpropan-2-olate. It is a white solid that is highly hygroscopic and air-sensitive, typically handled under an inert atmosphere. The molar mass is about 112.2 g/mol. It is often supplied as a solution in THF or as a dry solid in sealed containers.

KOtBu is a non-nucleophilic base: the bulky tert-butoxide group hinders nucleophilic attack, so deprotonation is favored over substitution. It readily abstracts protons from relatively weak carbon acids, enabling formation of enolates, acetylide anions, and other carbanions. It is commonly used to generate enolates from ketones and esters, promote E2 eliminations, and activate pronucleophiles for subsequent alkylations.

Handling and safety: KOtBu reacts with moisture and carbon dioxide in air, forming tert-butanol and related salts; it is caustic and can cause severe irritation. It should be stored under dry, inert conditions and used with appropriate PPE in a fume hood.

Applications: KOtBu is often employed in THF or DME as a robust base for deprotonation steps in synthetic sequences, in preparation of organometallic species, and in various cross-coupling or condensation protocols that require a strong, non-nucleophilic base.

See also: tert-butoxide, enolates, E2 eliminations.