Acid-Catalyzed Enolization of 2-Methylpropanal

Acid-Catalyzed Enolization of 2-Methylpropanal THE OVERALL REACTION  

Step 1 In aqueous solution, hydronium ion transfers a proton to the carbonyl oxygen. 

Step 2 A water molecule acts as a Brpnsted base to remove a proton from the a carbon of the protonated carbonyl. 

Lapworth reasoned that an enol was a reactive intermediate, that its formation was ratedetermining, and that the halogen didn t participate until after the rate-determining step. These early studies provided the basis for the generally accepted mechanism for the a-halogenation of aldehydes and ketones. 

Further, Lapworth s suggestion that enols are intermediates in these reactions has been established to apply to numerous other reactions of carbonyl compounds as well. Enols are intermediates in the hydration of alkynes (see Section 9.12) and the decarboxylation of P-keto acids and malonic acid derivatives (see Section 18.16). They are also intermediates in a number of biochemical processes including glucose metabolism and fatty acid biosynthesis. 

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