Tautomerism enol formation

Question

Acid catalysed  tautomerism and base catalysed 

Explain the mechanism of attack  using reagent D⁺ in acid catalysed and OD^- in base catalysed   (donot use bond line diagram) . What are the final ptoducts??

Answer 1

In the acid-catalyzed reaction, the molecule is first protonated on oxygen and then loses the C-H proton in a second step. When the enol form reverts to the keto – since this is an equilibrium process – it picks up a deuteron instead of a proton since the solution is D₂O. Also, the D+ (or H+ if water is the solvent) is regenerated at the end (catalyst).

In the base-catalyzed reaction, the C-H proton is removed first by the base (for example hydroxide ion OH^-, OD^- ) and the proton (or D⁺ in our case) added to the oxygen atom in a second step. Also, OD- (or OH- if water is the solvent) is regenerated at the end (catalyst).

The enolate ion generated from the enol (Fig. I.6) in the base-catalyzed mechanism is nucleophilic due to: Oxygen’s small atomic radius and Formal negative charge.