Which of the following best describes the difference between a ketone and an aldehyde?

• A. A ketone contains a nitrogen atom in its functional group, while an aldehyde does not.
• B. A ketone has a hydroxyl group $\left(OH\right)$ attached to a carbon, while an aldehyde has a carboxyl group.
• C. A ketone has a carbonyl group $(C=O)$ bonded to two carbon atoms, while an aldehyde has a carbonyl group bonded to at least one hydrogen atom.
• D. A ketone is always aromatic, while an aldehyde is always aliphatic.

Answer: (C)

Verified step by step guidance

1. Identify the functional groups involved in ketones and aldehydes. Both contain a carbonyl group, which is a carbon double-bonded to an oxygen, represented as \(\mathrm{C=O}\).
2. Understand the bonding environment of the carbonyl carbon in each compound: In a ketone, the carbonyl carbon is bonded to two carbon atoms, meaning it is flanked by alkyl or aryl groups on both sides.
3. In an aldehyde, the carbonyl carbon is bonded to at least one hydrogen atom and one carbon atom, distinguishing it from ketones.
4. Evaluate the incorrect options: Ketones do not contain nitrogen in their functional group, and neither ketones nor aldehydes have hydroxyl (\(\mathrm{OH}\)) or carboxyl (\(\mathrm{COOH}\)) groups as their defining feature.
5. Also, ketones and aldehydes can be either aromatic or aliphatic depending on their structure, so the statement about ketones always being aromatic and aldehydes always aliphatic is false.