Which of the following acids has the smallest dissociation constant?
Correct answer: C. BrCH₂CH₂COOH
- A. CH₃CHFCOOH
- B. FCH₂CH₂COOH
- C. BrCH₂CH₂COOH
- D. CH₃CHBrCOOH
Explanation
Br is less electronegative than F. BrCH₂CH₂COOH has the smallest dissociation constant (Ka) → i.e., it is the weakest acid.In CH₃CHBrCOOH the Br is on the α-carbon (the carbon directly next to the COOH). An electronegative substituent directly adjacent to the carboxyl group stabilizes the carboxylate anion strongly by the inductive (-I) effect, so the acid is stronger (larger KaK_aKa ).
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