Which of the following functional groups is characterized by a carbon-oxygen double bond? $C=O$

• A. Carbonyl group $C=O$
• B. Amino group $\mathrm{NH}{2}_{}$
• C. Hydroxyl group $\mathrm{OH}$
• D. Sulfhydryl group $\mathrm{SH}$

Answer: (A)

Verified step by step guidance

1. Identify the functional groups listed in the problem: Carbonyl group, Amino group, Hydroxyl group, and Sulfhydryl group.
2. Understand the structure of each functional group: A carbonyl group contains a carbon-oxygen double bond (C=O).
3. Recognize that the amino group is characterized by a nitrogen atom bonded to hydrogen atoms (NH2).
4. Note that the hydroxyl group consists of an oxygen atom bonded to a hydrogen atom (OH).
5. Understand that the sulfhydryl group contains a sulfur atom bonded to a hydrogen atom (SH).