Organic Chemistry MCAT Practice Exam

What is the outcome of an aldol condensation after the elimination step?

1. Aldehyde

2. Alcohol

3. α,β-unsaturated carbonyl compound

4. Carboxylic acid

The correct answer is: α,β-unsaturated carbonyl compound

In an aldol condensation reaction, the process begins with the formation of a β-hydroxy carbonyl compound (also known as an aldol) through the nucleophilic addition of an enolate ion to a carbonyl group. Following this initial step, dehydration occurs, resulting in the elimination of a water molecule. The key outcome of this dehydration step is the formation of an α,β-unsaturated carbonyl compound. This compound features a double bond between the α and β carbons adjacent to the carbonyl, and it is characterized by its increased stability due to conjugation between the double bond and the carbonyl group. This conjugation not only enhances the stability of the product but also affects its reactivity, making it an important intermediate in many organic reactions. In summary, after the elimination step in the aldol condensation, the final product is an α,β-unsaturated carbonyl compound, which is why this choice is the correct response.