A feature of organic compounds not found in inorganic compounds is the presence of which of the following?

• A. Ionic bonds between metal and nonmetal atoms
• B. Simple binary compounds like ${\mathrm{NaCl}}_1$
• C. Absence of carbon atoms
• D. Functional groups such as ${\mathrm{COOH}}_1$ (carboxyl) or ${\mathrm{OH}}_1$ (hydroxyl)

Answer: (D)

Verified step by step guidance

1. Understand that organic compounds are primarily characterized by the presence of carbon atoms bonded to hydrogen and other elements, forming a vast variety of structures.
2. Recognize that inorganic compounds often contain ionic bonds between metals and nonmetals, such as in simple binary compounds like NaCl, which are not typical features of organic compounds.
3. Identify that the unique feature of organic compounds is the presence of functional groups, which are specific groups of atoms within molecules that have characteristic properties and reactivities.
4. Note examples of common functional groups in organic chemistry, such as the carboxyl group (COOH) and the hydroxyl group (OH), which are responsible for the chemical behavior of many organic molecules.
5. Conclude that the presence of functional groups like COOH and OH distinguishes organic compounds from inorganic ones, making these groups a defining feature of organic chemistry.