Which of the following represents an amino group?

• A. ${\mathrm{OH}}_{\mathrm{}}$
• B. ${\mathrm{COOH}}_{\mathrm{}}$
• C. ${\mathrm{CHO}}_{\mathrm{}}$
• D. ${\mathrm{NH}}_2$

Answer: (D)

Verified step by step guidance

1. Understand that an amino group is a functional group commonly found in organic molecules, especially amino acids, and it consists of a nitrogen atom bonded to hydrogen atoms.
2. Recall the general formula for an amino group, which is \(\mathrm{NH_2}\), where nitrogen (N) is bonded to two hydrogen (H) atoms.
3. Analyze the given options: \(\mathrm{OH}\) represents a hydroxyl group, \(\mathrm{COOH}\) represents a carboxyl group, and \(\mathrm{CHO}\) represents an aldehyde group.
4. Compare these groups to the amino group and identify that none of the first three options contain nitrogen bonded to hydrogens, which is essential for an amino group.
5. Conclude that the correct representation of an amino group is \(\mathrm{NH_2}\), as it matches the definition and structure of the amino functional group.