The correct order of decreasing acidity of the following aliphatic acids is:

Question

The correct order of decreasing acidity of the following aliphatic acids is:

1. A. (CH3)3CCOOH (CH3)2CHCOOH CH3COOH HCOOH
2. B. CH3COOH (CH3)2CHCOOH (CH3)3CCOOH HCOOH
3. C. HCOOH CH3COOH (CH3)2CHCOOH (CH3)3CCOOH (Correct answer)
4. D. HCOOH (CH3)3CCOOH (CH3)2CHCOOH CH3COOH

Correct Answer

Option C — HCOOH CH3COOH (CH3)2CHCOOH (CH3)3CCOOH

Detailed Solution & Explanation

The correct answer is HCOOH > CH$_3$COOH > (CH$_3$)$_2$CHCOOH > (CH$_3$)$_3$CCOOH.

Key Points

• Electron-donating (+I) alkyl groups destabilise the carboxylate anion and decrease acidity.
• HCOOH has no alkyl group, so it is the strongest; adding more/bulkier alkyl groups steadily lowers acidity.
• Order of decreasing acidity: HCOOH > CH$_3$COOH > (CH$_3$)$_2$CHCOOH > (CH$_3$)$_3$CCOOH.