Which functional group is characteristic of aldehydes and distinguishes them from most other classes of organic compounds?

• A. An amino group ($\mathrm{NH}{2}_{}$)
• B. A carbonyl group bonded to at least one hydrogen atom ($\mathrm{CHO}$)
• C. A hydroxyl group ($\mathrm{OH}$)
• D. A carboxyl group ($\mathrm{COOH}$)

Answer: (B)

Verified step by step guidance

1. Understand that aldehydes are a class of organic compounds characterized by a specific functional group that differentiates them from others.
2. Recall that a carbonyl group consists of a carbon atom double-bonded to an oxygen atom, represented as \(\mathrm{C=O}\).
3. Recognize that in aldehydes, this carbonyl group is bonded to at least one hydrogen atom, which is a key distinguishing feature.
4. Compare this to other functional groups: amino group (\(\mathrm{NH_2}\)), hydroxyl group (\(\mathrm{OH}\)), and carboxyl group (\(\mathrm{COOH}\)), which are characteristic of amines, alcohols, and carboxylic acids respectively.
5. Conclude that the functional group characteristic of aldehydes is the carbonyl group bonded to at least one hydrogen atom, often written as \(\mathrm{CHO}\).