Question

Problem:Propose a mechanism for the following reaction. (Hint: Number the carbons to help you see where they end up in the product.)

Short answer

Answer

Step-by-step solution

Acid-catalyzed ester formation

Alcohol reacted with acids to form the ester using acid as a catalyze.

Methanol reacted with acetic acid in the presence of acid catalyze forms methyl acetate (ester) as shown below.

Formation of methyl acetate

Mechanism of ester formation

In the first step, protonation occurs on the double first carbon, resulting in the formation of the most stable tertiary carbocation.

In the second step, the pair of electrons from the second pie bonds provides the nucleophile that adds to the carbocation. As a result of this reaction, a stable six-membered ring formed with the ester functional group, forming the desired given ester.

The formation of the ester is shown below.

Mechanism of ester formation