AAMC FL Practice Exam

Which step involves the formation of the enolate ion in an aldol condensation?

1. Protonation

2. Nucleophilic attack

3. Deprotonation

4. Condensation

The correct answer is: Deprotonation

The formation of the enolate ion is a critical step in the aldol condensation process. In this step, a base abstracts a proton from the alpha carbon of a carbonyl compound, typically an aldehyde or a ketone. The removal of this proton creates the enolate ion, which is characterized by a negative charge on the carbon adjacent to the carbonyl carbon and a double bond between these two carbons. This enolate ion is highly nucleophilic, which allows it to attack another carbonyl carbon in a subsequent step. The formation of the enolate is essential because it sets the stage for the nucleophilic attack and ultimately leads to the aldol product. Without this deprotonation step to create the enolate, the aldol condensation would not proceed as the necessary nucleophile would not be generated. In contrast, the other steps such as protonation, nucleophilic attack, and condensation involve processes that occur after the enolate ion has already formed and do not themselves involve the generation of the enolate. Understanding the formation of the enolate ion helps visualize how the aldol condensation mechanism progresses and why deprotonation is a key initial step in this transformation.