Carboxylic Acids Question 53

Question: Which of the following acids has the smallest dissociation constant

[IIT-JEE (Screening) 2002]

Options:

A) $ CH_3CHFCOOH $

B) $ FCH_2CH_2COOH $

C) $ BrCH_2CH_2COOH $

D) $ CH_3CHBrCOOH $

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Answer:

Correct Answer: C

Solution:

$ BrCH_2CH_2COOH $ is least acidic or has less $ K _{a} $ i.e., dissociation constant. It is A due to lesser -I effect of Br than F and B Br atom further away form $ -COOH $ group.