POTASSIUM TERT-BUTOXIDE COMPLEXED WITH A MACROCYCLIC LIGAND FOR DETERMINATION OF AUTOPROTOLYSIS CONSTANT OF TERT-BUTANOL AND AS A TITRANT

The autoprotolysis constant of ferf-butanol (t-BuOH) has been found equal to 10-28,5 at 25 °C. The conductance of potassium tert-butoxide (KBuO) solutions is too small to yield a reliable value. The dissociation is greatly increased by complexing potassium with a 18-crown-6 ligand or, much more so, with [2.2.2] cryptand. The paH in such solutions was measured with the hydrogen electrode. E°(Ag) (vs. E°(H2)) in t-BuOH was found equal to +0.840 V. Decrease of the paH of butoxide solutions by the “acids ” and hydrogen bond donors water and methanol has been recorded. By adding a suitable 18-crown-6 ligand, precipitation of potassium salts during titration of mono-and diprotic acids in t-BuOH with KBuO is prevented. It is suggested to titrate very weak acids in DMSO with KBuO complexed with 18-crown-6. © 1979, American Chemical Society. All rights reserved.