Question

Which of the following is not a functional isomer pair (of each other)?

• A. Alcohol and ether
• B. Aldehyde and ketone
• C. Carboxylic acid and esters
• D. Alcohol and esters

Hint:

To be isomers, compounds must have the exact same molecular formula.
Alcohols have one oxygen atom (\(\text{O}_1\)) while esters have two oxygen atoms (\(\text{O}_2\)), making it impossible for them to be isomers.

Answer 1

The Correct Option is D

Step 1: Understanding the Question:
The question asks to identify which of the given pairs of organic compound classes do not act as functional isomers of one another.

Step 2: Key Formula or Approach:
Functional isomers are constitutional isomers that share the same molecular formula but contain different functional groups.

Step 3: Detailed Explanation:

• Let us evaluate each pair:
- Option (A): Alcohols and Ethers: Both share the general molecular formula \(\text{C}_n\text{H}_{2n+2}\text{O}\). For example, ethanol (\(\text{C}_2\text{H}_5\text{OH}\)) and dimethyl ether (\(\text{CH}_3\text{--O--CH}_3\)) are functional isomers.
- Option (B): Aldehydes and Ketones: Both share the general molecular formula \(\text{C}_n\text{H}_{2n}\text{O}\). For example, propanal (\(\text{C}_2\text{H}_5\text{CHO}\)) and acetone (\(\text{CH}_3\text{COCH}_3\)) are functional isomers.
- Option (C): Carboxylic acids and Esters: Both share the general molecular formula \(\text{C}_n\text{H}_{2n}\text{O}_2\). For example, ethanoic acid (\(\text{CH}_3\text{COOH}\)) and methyl formate (\(\text{HCOOCH}_3\)) are functional isomers.
- Option (D): Alcohols and Esters: Alcohols have the general formula \(\text{C}_n\text{H}_{2n+2}\text{O}\), whereas esters have the general formula \(\text{C}_n\text{H}_{2n}\text{O}_2\). Because their general formulas and hydrogen-to-oxygen ratios differ, they can never have the same molecular formula for any given number of carbon atoms. Thus, they cannot be functional isomers.


Step 4: Final Answer:
Alcohols and esters are not a functional isomer pair.