ChemistryNEET 2025Carboxylic acids: acidity and reactions

Aldehydes, Ketones and Carboxylic Acids

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

A. $(C H_{3})_{3} CCOOH > (C H_{3})_{2} CHCOOH > C H_{3} COOH > HCOOH$
B. $C H_{3} COOH > (C H_{3})_{2} CHCOOH > (C H_{3})_{3} CCOOH > HCOOH$
C. $HCOOH > C H_{3} COOH > (C H_{3})_{2} CHCOOH > (C H_{3})_{3} CCOOH$ ✓
D. $HCOOH > (C H_{3})_{3} CCOOH > (C H_{3})_{2} CHCOOH > C H_{3} COOH$

Solution

Alkyl groups are electron-releasing and destabilise the carboxylate anion, so acidity falls as alkyl substitution grows: $HCOOH > C H_{3} COOH > (C H_{3})_{2} CHCOOH > (C H_{3})_{3} CCOOH$ .

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