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

• A. Hydroxyl group $-O_H$
• B. Carboxyl group $-C_{O}OH$
• C. Amino group $-N_{H}2$
• D. Carbonyl group $C=O$

Answer: (A)

Verified step by step guidance

1. Identify the functional groups listed in the problem: hydroxyl group (−OH), carboxyl group (−COOH), amino group (−NH2), and carbonyl group (C=O).
2. Recall that alcohols are characterized by the presence of the hydroxyl group, which consists of an oxygen atom bonded to a hydrogen atom (−OH) attached to a saturated carbon atom.
3. Understand that the carboxyl group (−COOH) is characteristic of carboxylic acids, not alcohols; it contains both a carbonyl and a hydroxyl group bonded to the same carbon.
4. Recognize that the amino group (−NH2) is characteristic of amines and amino acids, involving nitrogen bonded to hydrogen atoms.
5. Note that the carbonyl group (C=O) is found in aldehydes and ketones, where a carbon atom is double bonded to oxygen, but it does not include the hydroxyl group that defines alcohols.