Which of the following functional groups is characteristic of thiols?

• A. Hydroxyl group ($OH$)
• B. Sulfhydryl group ($SH$)
• C. Amino group ($NH{2}_{}$)
• D. Carbonyl group ($CO$)

Answer: (B)

Verified step by step guidance

1. Step 1: Understand what a functional group is — it is a specific group of atoms within molecules that is responsible for the characteristic chemical reactions of those molecules.
2. Step 2: Identify the functional groups listed: Hydroxyl group (OH), Sulfhydryl group (SH), Amino group (NH₂), and Carbonyl group (CO).
3. Step 3: Recall that thiols are sulfur-containing analogs of alcohols, meaning they have a sulfur atom bonded to a hydrogen atom.
4. Step 4: Recognize that the functional group characteristic of thiols is the Sulfhydryl group, which is represented as -SH.
5. Step 5: Confirm that the Sulfhydryl group (-SH) distinguishes thiols from other functional groups like Hydroxyl (-OH), Amino (-NH₂), and Carbonyl (C=O).