Fire Hazard
Potassium tert-butoxide is a flammable solid.
It ignites on heating. Being very strongly
basic, its reactions with acids are highly
exothermic. Contact of solid powder with
drops of sulfuric acid and vapors of acetic
acid caused ignition after an induction period
of 0.5 and 3 minutes, respectively (Manwaring
1973). Ignition occurs upon reactions
with many common solvents of the
type ketone, lower alcohols, esters, and halogenated
hydrocarbons. Such solvents include
acetone, methyl ethyl ketone, methyl isobutyl
ketone, methanol, ethanol, n-propanol, isopropanol,
ethyl acetate, n-propyl formate,
n-butyl acetate, chloroform, methylene chloride,
carbon tetrachloride, epichlorohydrin,
dimethyl carbonate, and diethyl sulfate
(NFPA 1997). Such ignition may arise from
accidental contact of the alkoxide with these
solvents and may be attributed to sudden
release of energy from exothermic reactions.
However, slow mixing of the powder
with excess solvent will dissipate the
heat. It reacts violently with water, producing
tert-butanol and potassium hydroxide, as
follows:
K―OC―(C4H9)3＋H2O →
tert-C4H9OH +KOH
The addition of potassium tert-butoxide
to the solvent dimethyl sulfoxide can cause
ignition of the latter (Bretherick 1995).
Purification Methods
It sublimes at 220o/1mm. The last traces of tert-BuOH are removed by heating at 150-160o/2mm for 1hour. It is best prepared afresh as likely impurities are tert-BuOH, KOH and K2CO3 depending on its exposure to air. Its solubility at 25-26o in hexane, toluene, Et2O, and THF is 0.27%, 2.27%, 4.34% and 25.0%, respectively. [Feuer et.al. J Am Chem Soc 78 4364, Doering & Urban J Am Chem Soc 78 5938 1956, Beilstein 1 IV 1612.]
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