Which of the following acids has the smallest dissociation constant?

Which of the following acids has the smallest dissociation constant?
  1. $\mathrm{CH}_{3} \mathrm{CH}(\mathrm{F}) \mathrm{COOH}$
  2. $\mathrm{FCH}_{2} \mathrm{CH}_{2} \mathrm{COOH}$
  3. $\mathrm{BrCH}_{2} \mathrm{CH}_{2} \mathrm{COOH}$
  4. $\mathrm{CH}_{3} \mathrm{CH}(\mathrm{Br}) \mathrm{COOH}$

Solution

Bromine is less electronegative than $\mathrm{F}$, further in $\mathrm{BrCH}_{2} \mathrm{CH}_{2} \mathrm{COOH}, \mathrm{Br}$ is more away from the $-\mathrm{COOH}$ group than in $\mathrm{CH}_{3} \mathrm{CHBrCOOH}$.

Asked in: JEE-TOPICTESTS-CHEMISTRY

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