The protonation equilibrium of methyl ketones RCOCH3 (R = Me, Et, i-Pr, t-Bu) and of di-t-butyl ketone have been investigated in aqueous sulfuric acid at 25 C by means of UV and NMR spectroscopies. Both techniques yield experimental points which display systematic differences from theoretical curves. The various possible sources of perturbation are discussed, and it is concluded that a specific interaction of ther ketone molecules with the hydronium ion is responsible for the observed deviations. A solution to this two-equilibrium system is presented, which yields m* and pK values of 0.35 and -3.06, respectively, for acetone (see eq. (5) in the text for the explanation of symbols). Similar values are found for the other methyl ketones, and very different values (0.85 and -7.24, respectively) for di-t-butyl ketone.
The Influence of Hydration on the Protonation Equilibria of Aliphatic Ketones in Aqueous Sulfuric Acid
BAGNO, ALESSANDRO;SCORRANO, GIANFRANCO
1987
Abstract
The protonation equilibrium of methyl ketones RCOCH3 (R = Me, Et, i-Pr, t-Bu) and of di-t-butyl ketone have been investigated in aqueous sulfuric acid at 25 C by means of UV and NMR spectroscopies. Both techniques yield experimental points which display systematic differences from theoretical curves. The various possible sources of perturbation are discussed, and it is concluded that a specific interaction of ther ketone molecules with the hydronium ion is responsible for the observed deviations. A solution to this two-equilibrium system is presented, which yields m* and pK values of 0.35 and -3.06, respectively, for acetone (see eq. (5) in the text for the explanation of symbols). Similar values are found for the other methyl ketones, and very different values (0.85 and -7.24, respectively) for di-t-butyl ketone.Pubblicazioni consigliate
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