Question

Which of the following compounds forms \(4\)-Methylpent-\(3\)-en-\(2\)-one by aldol condensation on further dehydration.

• A. Two molecules of acetone
• B. Two molecules of acetaldehyde
• C. Acetaldehyde and formaldehyde
• D. Acetaldehyde and acetone

Hint:

Two molecules of acetone undergo aldol condensation and then dehydrate to mesityl oxide.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept
Aldol condensation joins two carbonyl molecules to a beta-hydroxy carbonyl, which then loses water.

Step 2: Work Backwards
The product \((\text{CH}_{3})_{2}\text{C}=\text{CH}-\text{CO}-\text{CH}_{3}\) has six carbons, so the reactants together supply six carbons: two acetone molecules (3+3).

Step 3: Forward Reaction
Two acetone molecules give diacetone alcohol, \((\text{CH}_{3})_{2}\text{C(OH)}\text{CH}_{2}\text{COCH}_{3}\).
Dehydration gives 4-methylpent-3-en-2-one.

Final Answer:
Two molecules of acetone give the product, option (A). \[ \boxed{\text{(A) }\text{Two molecules of acetone}} \]