Which of the following functional groups can be synthesized using only $C_2{H}_2$ (acetylene) as the source of carbon atoms?

• A. Ether
• B. Carboxylic acid
• C. Aromatic ring
• D. Alcohol

Answer: (D)

Verified step by step guidance

1. Step 1: Understand the starting material, acetylene (C\_2H\_2), which is a simple alkyne with a triple bond between two carbon atoms. It can undergo various reactions to build more complex molecules.
2. Step 2: Analyze the functional groups listed: ether, carboxylic acid, aromatic ring, and alcohol. Consider the carbon framework and heteroatoms (like oxygen) required for each group.
3. Step 3: Recall that acetylene can be hydrated (addition of water) in the presence of acid and mercury(II) catalyst to form an enol intermediate, which tautomerizes to a ketone or aldehyde. This intermediate can be further reduced or modified to form an alcohol.
4. Step 4: Recognize that synthesizing ethers, carboxylic acids, or aromatic rings directly from acetylene alone is more complex and typically requires additional carbon sources or reagents beyond acetylene itself.
5. Step 5: Conclude that among the options, alcohols can be synthesized using only acetylene as the carbon source through hydration and subsequent transformations, making alcohol the correct answer.