Which of the following carbonyl compounds on condensation gives an aromatic compound?

Options

A. `CH_3CHO`
B. HCHO
C. `CH_3COCH_3`
D. `CH_3CH_2CHO`

Answer

To determine which carbonyl compound on condensation gives an aromatic compound, we can analyze the given options.

### Step-by-Step Solution:

1. **Identify Carbonyl Compounds**: The first step is to list the carbonyl compounds provided in the question. Common carbonyl compounds include aldehydes and ketones.

2. **Understand Condensation Reaction**: A condensation reaction typically involves the combination of two molecules with the elimination of a small molecule, often water. In this case, we are looking for a reaction that leads to the formation of an aromatic compound.

3. **Consider Acetone as a Candidate**: One of the common carbonyl compounds is acetone (CH3COCH3). When acetone undergoes condensation in the presence of a strong acid like concentrated H2SO4, it can lead to the formation of mesitylene (1,3,5-trimethylbenzene).

4. **Reaction Mechanism**: The condensation of acetone involves the formation of a new carbon-carbon bond, leading to the creation of a compound with a benzene ring. During this process, three molecules of water are eliminated.

5. **Check Aromaticity**: The product, mesitylene, contains a benzene ring. To confirm its aromatic nature, we can apply Huckel's rule, which states that a compound is aromatic if it has (4n + 2) π electrons. In mesitylene, the benzene ring contributes 6 π electrons (from the three double bonds), satisfying the rule for n=1.

6. **Conclusion**: Therefore, the carbonyl compound that gives an aromatic compound upon condensation is acetone, leading to the formation of mesitylene.

### Final Answer:
The carbonyl compound that gives an aromatic compound on condensation is **acetone**.