Butoxide

Butoxide refers to the alkoxide ion derived from butane alcohols, and generally denotes the family of alkoxide reagents with a four-carbon substituent. The basic formula is RO−, where R is a butyl group: n-butyl (n-Bu), sec-butyl (butan-2-yl), or tert-butyl (tert-Bu). The most widely used members are the salts of tert-butoxide, such as sodium tert-butoxide (NaOtBu) and potassium tert-butoxide (KOtBu). Other butoxide variants include sodium butoxide (NaOBu, from butan-1-ol) and related sec-butoxide salts, though these are less common as bases than the tert-butoxide derivatives.

Preparation typically involves deprotonation of the corresponding butanol with a strong base (for example, NaH or Na metal) or metathesis of a metal alkoxide with a suitable salt. Alkoxide salts are typically moisture- and air-sensitive and are usually handled in anhydrous organic solvents such as THF or toluene.

Properties and roles: butoxides are strong bases, with tert-butoxide derivatives being particularly bulky and non-nucleophilic. This makes KOtBu and NaOtBu popular for promoting eliminations (E2) and for deprotonations in sensitive substrates where nucleophilic side reactions must be minimized. n-Butoxide and sec-butoxide can also act as bases and, in some cases, as nucleophiles, depending on the substrate and solvent.

Safety: alkoxide reagents react readily with water and atmospheric CO2, releasing alcohol and forming hydroxides; they are caustic and should be handled with appropriate protective equipment under inert or anhydrous conditions.