Question

Which of the following is the formula of the third higher homologue of \(\text{CH}_{3}\text{-CH}_{2}\text{-COOH}\)?

• A. \(\text{CH}_{3}\text{-CH}_{2}\text{-CH}_{2}\text{-COOH}\)
• B. \(\text{CH}_{3}\text{-CH}_{2}\text{-CH}_{2}\text{-CH}_{2}\text{-COOH}\)
• C. \(\text{CH}_{3}\text{-CH}_{2}\text{-CH}_{2}\text{-CH}_{2}\text{-CH}_{2}\text{-COOH}\)
• D. \(\text{CH}_{3}\text{-CH}_{2}\text{-CH}_{2}\text{-CH}_{2}\text{-CH}_{2}\text{-CH}_{2}\text{-COOH}\)

Hint:

Each higher homologue adds one CH2 group, so the third higher homologue of a 3-carbon acid has 6 carbons.

Answer 1

The Correct Option is C

Step 1: Approach
Add three $\text{CH}_2$ groups to $\text{C}_3\text{H}_6\text{O}_2$ to get $\text{C}_6\text{H}_{12}\text{O}_2$.

Step 2: Counting carbons in the options
Option (A) has 4 carbons, option (B) has 5 carbons, option (C) has 6 carbons, option (D) has 7 carbons.

Step 3: Conclusion
Only option (C) has 6 carbons, so it is the third higher homologue.

Final Answer:
The correct formula is that of hexanoic acid. \[ \boxed{\text{(C) }\text{CH}_{3}\text{-CH}_{2}\text{-CH}_{2}\text{-CH}_{2}\text{-CH}_{2}\text{-COOH}} \]