tertButoxide

tert-butoxide is the tert-butoxide anion, (CH3)3CO−, the conjugate base of tert-butanol. It is most commonly encountered as its salts, especially potassium tert-butoxide (KOtBu) and sodium tert-butoxide (NaOtBu). These reagents are widely used as strong, bulky bases in organic synthesis.

Preparation and handling: tert-Butoxides are typically prepared by deprotonating tert-butanol with a strong base or via salt metathesis, and are sold as dry solids or solutions in hydrocarbon solvents. They are highly moisture sensitive and must be stored under dry, inert conditions to prevent hydrolysis and the formation of tert-butanol.

Properties: The tert-butoxide anion is a strong, non-nucleophilic base due to steric hindrance from the tert-butyl group. Its conjugate acid is tert-butanol. In common organic solvents, tert-butanol has a pKa around the mid-teens, making tert-butoxide capable of deprotonating relatively weak acids while remaining a poor nucleophile because of its bulk.

Applications: KOtBu and NaOtBu are used to generate enolates from carbonyl compounds, promote eliminations (E2) over substitutions in alkyl halides, and deprotonate weak C-H bonds in various syntheses. The bulky nature of tert-butoxide favors elimination and deprotonation pathways while limiting nucleophilic substitution.

Safety: tert-Butoxides react with water and air, forming tert-butanol and corresponding hydroxide salts; they are caustic and irritant. Handling requires dry, inert conditions, appropriate protective equipment, and careful exclusion of moisture.